i try to download a app and it tells me my apple id is disconnected

Do you mean 'disconnected' or disabled ?

If the former, what is the full text of the message.

If the latter try resetting its password (and then logging out and back in everywhere) : If your Apple ID has been locked - Apple Support

If that doesn't fix it contact iTunes Support and see if they can/will re-enable it : https://www.apple.com/emea/support/itunes/contact.html