I have problems with the APP connecting to Steam, EA and it also fails to update my list of Epic games.

On Steam I can log in and everything seems to be going well, but then it fails.
On EA I can't connect to my account and no, it's not because I forgot my password.
Ubisoft Connect always fails
Epic games is the one that gives me the least problems

I have also noticed that GOG recognizes my Steam achievements, as well as my Steam tags, but the Tags it has are very old, not the ones I currently use on my Steam account that are more organized, I don't know how I can configure that, THEY ARE REALLY VERY USEFUL because I have several games of different genres and I can't organize them correctly.

Epic is an official integration. Open a support ticket for whatever issues you're having with it.

For the rest, follow the steps in the thread below, if you haven't already done so. If you're still having issues, post in that thread and hope someone can help.
https://www.gog.com/forum/general_beta_gog_galaxy_2.0/gog_galaxy_community_integrations_heres_how_to_fix_them_steam_ea_etc