Q: Apple ID

Here's the situation i'm in, when i first launch iTunes, it always said with a warning that you don't have enough access privilages, i tried to change the music settings to read and write but it didn't work, then, i tried to log in to my apple ID account and it said it can't complete this action even though i have tried with a different password(i didn't forget my pass)it also applies to all the apps that requires Apple ID. Pls help me, this problem starts when OS X Sierra was released for the 1st time. Thx in Advance.