I have this issue also for a while now.
Its now always but lot of times it gets stuck at 90% exactly while it is trying to log in and then it gets stuck.
You have to open taskmanager kill the uefn process and start uefn again.
Sometimes the Epic Games Launcher (EPGL) needs uninstalling using Windows 11 Uninstall and a new version downloaded and installed as EPGL cannot correctly load the new latest version of UEFN. USUALLY EPGL not UEFN.
Epic cannot permanently fix this as its a Windows 11 Security problem
This issue usually happens due to server delays, cache problems, or network interruptions. Try refreshing the page, clearing cache, or checking your internet connection to resolve the login stuck at 90% problem.