"The data couldn’t be read because it isn’t in the correct format"

The data couldn’t be read because it isn’t in the correct format.

I keep getting this notice when I try to log in to App Store.

can you please help. I have spent a lot of money on this Mac book for my child and he cant use all the features because of this problem. its annoying and I can't afford to buy a new one for him.

I've been having this problem since I have bought this Mac book please help.

[Re-Titled by Moderator]