I will drop some tips and see if you done one of them or try them, couldn't grab much from the replies but mostly:
-Make sure your antivirus doesn't delete or block your RageMP files, if so, make an exception to allow it.
-Make sure your firewall permissions allows the client to run in private or public connections.
-Make sure of your internet speed is reliable for the client to run and launch.
-Re-install RageMP by going to Ragemp directory, select all files except the updater, delete them and run the updater as administrator.
-Make sure your game runs smoothly in single player.
-if you got the game files but not installed, or you purchased the game from epic and want it to recognize the old files you got which you downloaded from other sources, see
this video or search for one you can understand better in avoiding to download 90 GBs.
-Try to run a check on your windows updates and drivers.
-Restart after major changes, to take effect.
Note: Most of what i said, is my normal routine when i face a problem with the game or client.