I bought a premium minecraft, but earlier on the same account I played no - premium and now as I want to enter the server I have to log in even though I have premium and as I play on some launcher supporting premium accounts such as feather or lunar or lab mod I do not have a launcher logo over my head (in the case of lunar or feather) and on the feather I can not use voice chat. 
This is so on the servers I played on as I did not have Premium Minecraft.