This is intended. Simply working off your punishment isn't enough for you to be eligible to earn hextech loot. You need to play games with positive behavior in order to start earning hextech loot. How long you have to wait/how many games you need to play is uncertain, though. It's not a fixed amount of times for everyone, the wait time will be different from player to player. Also, the harsher your punishment was (such as a temporary ban vs. a chat restriction), the longer you will have to wait.
All I can say is to play games with positive behavior and eventually you will be able to earn hextech loot.