Been a couple days I tried to log online. What's going on with this?

It seems to be working fine for me, been playing on there all weekend and it also went fine.
A couple things to check:
- Make sure you are using the classic game version not the enhanced one
- You need CD key configured (you can do that within launcher)
- Check that your port 6112-6119 is opened both on UDP/TCP and that you have an IPV4 (sadly game does not work with IPV6 yet)
- Make sure your connection speed is ok (game does a ping to the server and if it is too low you wont be able to create or join game although you are able to login.

Hopefully this was helpful.

If you are running into problems connecting to Bnet make sure to send tickets to Blizzard Bnet support annoying them about these issues may be the only way we get better support for nat and ipv6.

Yes all of that is in order. I played before and connected there should not be any issue but somehow it leads to this and game breaks.

Ok so what it looks like is happening is your client may crash because of the awkward way bnet was implemented back then.

Are you playing through Linux wine? If yes you may need to delete .wine in home and reinstall a fresh installation afterward.
Also you may want to check the ddraw.dll library you are using some may not be compatible.
I am personally using an older version of the now famous cnc-ddraw you can find that on github it works pretty well.

Hopefully this helps.

No I'm on Windows 11.

3rd application interference game window. With some own overlay most likely.
https://support.gog.com/hc/en-us/articles/360019811033-Diablo-missing-menu-text?product=

There is way to check which one apps interfer the game. Simple way (but not guaranteed to show everything, Task Manager are trash since Win8 although UI are better) - Task Manager - target exe - Analyze Wait Chain.

Or close every apps. Non-driver but bundled - first to be closed (terminated) or removed. They are not part of the drivers.