Had a quick scroll through but couldn't find anyone else with this issue.
I use Sdonate to add points to players and get multiple errors saying "Player not found" if they are not in game. Even if I try to add manually with /sr add I still get the same issue. I have tried player name and steam id but still won't work until they're online. Doesn't happen with all players.

Something i'm doing wrong or a bug?

Got the same issue. What I did was give players bleach who they can sell for RP

Thanks. Good idea

Hi there i found if you are using any clan plug you will have to use "[clananame] PlayerName" and it will work.
hope this helps.