my account is over 18 and it wont allow me to join a realm

i have been invite to a realm and when i accept the invite Minecraft says my account is not set up properly but i have joined it in the past but then when i logged in it would just give me a purple nether portal screen with building terrain and then i tried logging off and on and then i tried leaving the realm and then re-joining it and then it said my account is not sett up properly

thanks for your time