Garena Login problem only occurs when Garena servers are on overload, suffering a DDoS attack or Garena admins are updating their user database which sometimes cause the user unable to login their accounts from the client (for e.g. Stuck at Garena Authenticating, checking client version). Players who have logged in before this maintenance update are still connected to server.
The only solution is to wait till Garena servers get fixed.
If you still can't login Garena account from your PC, you can login from other internet connection/PC to verify if the issue is server or client sided. If it's problem from your side, you can try doing the following:
1. Pick another server from Garena login window and try to login.
2. Allow Garena to your network firewall safe-list.
3. Open Garena folder (c:\Program Files\Garena) and delete the files inside Cache and User folder (this works on most cases)
4. Completely delete Garena folder and download/install the latest version from Garena website.
5. Check if your Anti-virus program is blocking Garena.exe from connecting.
6. Reinstall your windows
These are some tips for fixing Garena login problem, if the problem still persist try contacting your Internet service provider and Garena support.