My iTunes has been disabled

What do you mean by iTunes is disabled? Did you just upgrade your Mac to macOS Catalina or macOS Big Sur and cannot find iTunes? If yes, this is because iTunes is no longer available on modern Mac operating systems. Finder does all the work iTunes used to do.

Else, what do you mean by iTunes has been disabled? Please elaborate.

And I see that you have mentioned iPhone 8 Plus. iTunes is not available on iPhone. It is available on Mac and Windows PC. Maybe here you mean 'iTunes Store has been disabled on your iPhone 8 Plus.' If this is the case, follow the steps below.

Note: If you are a child, you cannot follow these steps. Your parent/guardian can.

1. Open iPhone Settings and tap Screen Time.
2. Tap Content & Privacy Restrictions.
3. Tap iTunes & App Store Purchases and make sure Installing, Deleting, and In-app purchases are allowed.
4. Next, go back and tap Allowed Apps.
5. Make sure the switch for iTunes Store is green.

Hope it helps. If not, please be specific, and I will try to reply again.

If you see a message that says 'Your account has been disabled in the App Store and iTunes',  contact Apple Support for help.