lucioghosty: This is the solution! Thank you so much! I was able to log in with PSN after this solution.

Bustacap: workaround until they fix it:

- close GOG Galaxy if it's running at the moment

- log in to PSN (store.playstation.com) through your browser
(if you were already logged in, log out first, then back in)

- after the login open this link: https://ca.account.sony.com/api/v1/ssocookie

youll get something like: {"npsso":"xxx"}
where xxx is the npsso value

- open windows explorer and enter the following into the address bar at the top and press enter
%LocalAppData%\GOG.com\Galaxy\plugins\installed\

- open the psn_{random number} folder and edit the plugin.py file with your favourite text editor

- go to line 64. it sould look like this:
stored_npsso = stored_credentials.get("npsso") if stored_credentials else None

delete everything on that line after: stored_npsso =
then add your nppso value behind it in quotation marks.

it should look like this:
stored_npsso = "npsso value"

("npsso value" is the value from step 3 and should be a 64 character long text consisting of numbers, lower case letters and upper case letters)
(the quotation marks " " are important!)

- save the changes made to plugin.py and close the file
- restart GOG Galaxy
- try connecting with PSN again

Red1142: I can't find the folder for playstation

Bustacap: workaround until they fix it:

- close GOG Galaxy if it's running at the moment

- log in to PSN (store.playstation.com) through your browser
(if you were already logged in, log out first, then back in)

- after the login open this link: https://ca.account.sony.com/api/v1/ssocookie

youll get something like: {"npsso":"xxx"}
where xxx is the npsso value

- open windows explorer and enter the following into the address bar at the top and press enter
%LocalAppData%\GOG.com\Galaxy\plugins\installed\

- open the psn_{random number} folder and edit the plugin.py file with your favourite text editor

- go to line 64. it sould look like this:
stored_npsso = stored_credentials.get("npsso") if stored_credentials else None

delete everything on that line after: stored_npsso =
then add your nppso value behind it in quotation marks.

it should look like this:
stored_npsso = "npsso value"

("npsso value" is the value from step 3 and should be a 64 character long text consisting of numbers, lower case letters and upper case letters)
(the quotation marks " " are important!)

- save the changes made to plugin.py and close the file
- restart GOG Galaxy
- try connecting with PSN again

Bustacap: workaround until they fix it:

- close GOG Galaxy if it's running at the moment

- log in to PSN (store.playstation.com) through your browser
(if you were already logged in, log out first, then back in)

- after the login open this link: https://ca.account.sony.com/api/v1/ssocookie

youll get something like: {"npsso":"xxx"}
where xxx is the npsso value

- open windows explorer and enter the following into the address bar at the top and press enter
%LocalAppData%\GOG.com\Galaxy\plugins\installed\

- open the psn_{random number} folder and edit the plugin.py file with your favourite text editor

- go to line 64. it sould look like this:
stored_npsso = stored_credentials.get("npsso") if stored_credentials else None

delete everything on that line after: stored_npsso =
then add your nppso value behind it in quotation marks.

it should look like this:
stored_npsso = "npsso value"

("npsso value" is the value from step 3 and should be a 64 character long text consisting of numbers, lower case letters and upper case letters)
(the quotation marks " " are important!)

- save the changes made to plugin.py and close the file
- restart GOG Galaxy
- try connecting with PSN again

chung2: Still no games in Library. Has anyone found a way to fix this??

DankAngel1664: It keeps showing me "Offline retry" any suggestions?

pyroguy7: I'm also getting this error.

goodvanilla: I figured what made the darn thing NOT work and do the plugin crash , was because I had no basic knowledge of python and did not know what a correct line/section should look like.

What can throw you off and make you do the lines wrong is this sentence "delete everything on that line after" from Bustacaps helping post.
You have to make sure the couple of lines to that WHOLE SECTION is deleted, not just a single line

I am talking about this
"original section looks like

async def authenticate(self, stored_credentials=None):
stored_npsso = stored_credentials.get("npsso") if stored_credentials else None
if not stored_npsso:
return NextStep("web_session", AUTH_PARAMS)

AFTER your edit the section should look like this

async def authenticate(self, stored_credentials=None):
stored_npsso = "xxxxxxxxxxxyournumbersherexxxxxxxxx"

And nothing else ! not the next lines and not even the : at the end.

I hope it made it clear , and help you other people who like me had no idea :)

Kosiarz2039: Hey you link on step 3 after the login open this link: https://ca.account.sony.com/api/v1/ssocookie but i have error when i open this link can you help?
{"error":"invalid_grant","error_description":"Invalid login","error_code":20,"docs":"[url=https://auth.api.sonyentertainmentnetwork.com/docs/","parameters]https://auth.api.sonyentertainmentnetwork.com/docs/","parameters[/url]":[]}
this is the error

Bustacap: reposting the newest version of the workaround for better visibility
----------------------

- close GOG Galaxy if it's running at the moment

- log in to the Playstation Store (store.playstation.com) through your browser
(if you were already logged in, log out first, then back in)

- after the login open this link: https://ca.account.sony.com/api/v1/ssocookie

youll get something like: {"npsso":"xxx"}
where xxx is the npsso value

(example of what it should look like: https://abload.de/img/npssomcj9f.png )

- open windows explorer and enter the following into the address bar at the top and press enter
%LocalAppData%\GOG.com\Galaxy\plugins\installed\

( https://abload.de/img/localappdataojjbg.png )

- open the psn_{random number} folder and edit the plugin.py file with your favourite text editor

- go to line 64. it sould look like this:
stored_npsso = stored_credentials.get("npsso") if stored_credentials else None

delete everything on that line after: stored_npsso =
then add your npsso value behind it in quotation marks.

it should look like this:
stored_npsso = "npsso value"

("npsso value" is the value from step 3 and should be a 64 character long text consisting of numbers, lower case letters and upper case letters)
(the quotation marks " " are important!)

(example of what it should look like: https://abload.de/img/plugingrjah.png )

- save the changes made to plugin.py and close the file
- restart GOG Galaxy
- try connecting with PSN again

Bustacap: workaround until they fix it:

- close GOG Galaxy if it's running at the moment

- log in to PSN (store.playstation.com) through your browser
(if you were already logged in, log out first, then back in)

- after the login open this link: https://ca.account.sony.com/api/v1/ssocookie

youll get something like: {"npsso":"xxx"}
where xxx is the npsso value

- open windows explorer and enter the following into the address bar at the top and press enter
%LocalAppData%\GOG.com\Galaxy\plugins\installed\

- open the psn_{random number} folder and edit the plugin.py file with your favourite text editor

- go to line 64. it sould look like this:
stored_npsso = stored_credentials.get("npsso") if stored_credentials else None

delete everything on that line after: stored_npsso =
then add your nppso value behind it in quotation marks.

it should look like this:
stored_npsso = "npsso value"

("npsso value" is the value from step 3 and should be a 64 character long text consisting of numbers, lower case letters and upper case letters)
(the quotation marks " " are important!)

- save the changes made to plugin.py and close the file
- restart GOG Galaxy
- try connecting with PSN again

Bustacap: workaround until they fix it:

- close GOG Galaxy if it's running at the moment

- log in to PSN (store.playstation.com) through your browser
(if you were already logged in, log out first, then back in)

- after the login open this link: https://ca.account.sony.com/api/v1/ssocookie

youll get something like: {"npsso":"xxx"}
where xxx is the npsso value

- open windows explorer and enter the following into the address bar at the top and press enter
%LocalAppData%\GOG.com\Galaxy\plugins\installed\

- open the psn_{random number} folder and edit the plugin.py file with your favourite text editor

- go to line 64. it sould look like this:
stored_npsso = stored_credentials.get("npsso") if stored_credentials else None

delete everything on that line after: stored_npsso =
then add your nppso value behind it in quotation marks.

it should look like this:
stored_npsso = "npsso value"

("npsso value" is the value from step 3 and should be a 64 character long text consisting of numbers, lower case letters and upper case letters)
(the quotation marks " " are important!)

- save the changes made to plugin.py and close the file
- restart GOG Galaxy
- try connecting with PSN again