Can't login into my iTunes nor my app store any suggestions?

Suggestions would be easier to make if you provide more details.

You can't sign in to the stores? That is what Log In means to me. A log in is a sign in so you are saying that the stores will not accept your password? You can't use your Apple ID to Log In?

Or do you mean that the apps will not work at all for you? You are signed in but when you attempt to purchase nothing happens?

Are you getting any error messages? Share some more details????

I can't sign into the Mac app store from my mini. Everything else works fine (iTunes store, icloud.com) and I can log in to the Mac app store (and everything else too) on my Air. So, it's just the Mac app store from my mini.

I rebooted. I deleted the "storeagent" preferences file. Still won't work. It just says "unknown error."

Came here from a google search and didn't realize this is for the iPad. So, never mind....

OK. That makes more sense now.

But anyway .....Did you try signing out of tha account completely by clicking on your ID and sign out? Then restart the Mac and try signing in again?