How do I fix this? I need a step by step noob friendly explanation. Maybe someone can Discord and help me or do it here on the forum?

I get this too. We we're going to have to be paiten until they fix it.

Tried everything. No luck.

You need to forward the ports through your router by entering the router settings through your browser.

Ok so I actually logged into the game. I did the port forwarding trough my router as well as did the Blizzard instructions for the Firewall. So the problem is me creating the game and people can't join it, says the Latency is too high. However some people can create a game and when I join them it actually works, so I select New Game and create a game and now people can join me as well UNTIL I quit Diablo. When I start the game again it stops working.

It is a total FLUE if you can Join or Create a game with people joining you. Blizzard and GOG need to fix this. This is bad on their end!

I have the same issue. Can log in, but cant host or join games. I made sure my ports are forwarded too in my router.

Same here. I followed the firewall instructions and no luck. I don't know how to " forward the ports through your router by entering the router settings through your browser"

please let me know if you guys figure it out or can help me thanks

Unite to destroy Diablo - up to 4 players can band together via Internet, or play head-to-head via direct IP. <-- This is what the description says about the game. I cannot seem to find any way to connect via direct IP nor can I play through Battle.net as long as Blizzard don't fix this problem (which has been an issue for years). Please do what you can from your end to fix this!

I have had no success getting any help from Blizzard Technical Support, they are that awful and I lost all hope. One time they advised me to mess with my graphics card when I had issues in StarCraft 2 Nova Covert Ops which led to my GPU melting cause of their overclocking instructions. They then suggested I reinstall Windows and to top it all off and rub more salt into the wound they asked me to check if my Internet was working while I was speaking to them on the online chat...

Only hope we have is for GOG to fix this, Blizz are washed up and can't do anything right anymore...

P.S

I only ever have technical issues with Blizzard games. Everything else seems to work just fine :)

Same here I tried everything and it still doesn't work. PORT forwarding and everything.

What exactly has been addressed?!
The post you linked to is a topic without any solution or official response. The blue text quote was copied there by some random dude, and the response he quoted comes from a topic about Diablo 2 Ladder Reset from 2017. It has nothing to do with Diablo 1, or with 2019's "Global" version of Battle.net functionality.

I've opened up ports 6112-6119, TCP & UDP on my Router.
I've opened up ports 6112-6119 TCP & UDP, plus 3724 TCP on my Firewall.
Still, nothing, Any help?

Try to connect to Battle.net, at this point you will probably get the error message. Exit Battle.net and return to the main menu and try to connect once again (this might require 2-4 tries).