iTunes

Try to log-out from iTunes then log back in with the new password.

If you recently changed your Apple ID or password, you might have to sign out and sign back in. To sign in on your iOS device, go to Settings > [your photo] > iTunes & App Store. Tap your Apple ID, sign out, then tap Sign In to log in again. Learn how to sign out on your Mac, PC, or Apple TV.(**according to apple at :https://support.apple.com/en-us/HT201400)

Hope you'll solve it!

Best regards!

If you have changed your ID or password, have you followed the steps in this article?

What to do after you change your Apple ID or password - Apple Support     

You must be fare more specific in describing your troubles.

Normally, after changing Apple ID password every service on every device that uses it must be updated with the new password.