game paid for but it says play demo and when i go onto any servers it says restart and when i do it does nothing

so when i load the minecraft launcher it says play demo although the game is fully paid for and when i go into minecraft it is like the full game but when i try go onto a server like hypixel or calamitymc i just cant because it says that i need to restart and when i do it happens again and i deleted the minecraft launcher and reinstalled and it fixed nothing