Have you done as the message tells you to do and contacted iTunes Support (these are user-to-user forums) ?
Or you might be able to re-enable it yourself, depending upon why it's been disabled e.g. if it’s been disabled for security reasons then resetting the password might fix it : If your Apple ID has been locked - Apple Support
You might then need to log out and back into your account wherever you're using it : What to do after you change your Apple ID email address or password - Apple Support
If that doesn't fix it then contact iTunes Support