If you're having trouble logging in, check the following:
- are you sure you chose the correct server? (US,EUW,EUNE...)
- make sure your username is correct, sometimes your username can be different than your summoner name (if you changed your summoner name for example)
- make sure you enter the correct password. A lot of times mis-typing is the culprit.
- make sure your login works on the LoL desktop app (game)
- NOTE: Sometimes PVP.NET is just down and may take a few minutes before coming back up.
If you're still having trouble, contact support and we can check into it with you.