Can’t log in to iTunes Store or get any apps

The resolution to this issue is often making sure you have entered a credit card or other valid method of payment* even if you don't plan on needing to use it. The document 'If you can't remove your last payment method or use no payment method with your Apple ID' ( https://support.apple.com/HT203905 ) mentions, "if you're using an existing Apple ID with the App Store for the first time, you must provide payment information."

If there is an option to select "Review" or "Continue", select that and enter valid payment information if required. If there's problems doing this:

On a mobile device tap: Settings > [your name at the top] > Media & Purchases > View Account > Review Apple ID.

Alternatively this document explains how to 'Change, add, [review,] or remove Apple ID payment methods' on an Apple mobile device, a Mac, or a PC; click here --> https://support.apple.com/HT201266

More things to try in this 2018 post by Urquhart1244 marked Apple Recommended:

https://discussions.apple.com/thread/8434425?answerId=33542414022#33542414022

If you continue to have problems contact Official Apple Support - Select your region from the list and then your country from the pop-up window. If you do not see your country, see if there is an "other" listing for that region.

https://getsupport.apple.com/?caller=cups&PGF=PGF63005

*Payment methods that you can use with your Apple ID - https://support.apple.com/HT202631

I suggest you also send feedback to Apple about the looping issue. I see this posted at least daily and while there is a workaround, it's clearly a feature that is not working for everybody, or needs better explaining. Try entering your Apple ID email address and see if it then prompts for a password. If this works, please let me know, but according to this user it won't --> https://discussions.apple.com/thread/253412678?answerId=256387736022#256387736022.

Click on this link for Apple products feedback links --> http://www.apple.com/feedback/

Hello turnip131,

Thank you for posting in the Apple Support Communities. We understand that you're seeing an Apple ID sign in loop after restoring the iPhone and creating a new Apple ID. We'd like to help.

First, let's be sure the steps in the support article below were taken to sign in to your iPhone. To sign in to your device, tap on Settings > Sign in to your iPhone. Keep in mind that we recommend everyone have only one Apple ID for all Apple devices and services. This is because Apple ID purchases and content can't be merged from an old Apple ID to a new one.

Sign in with your Apple ID

From there, try logging into your Apple ID account from a web browser. This step often helps identify Apple ID or password issues. You can also see if any other account-related prompts appear there, that might help resolve the issue you're experiencing with the iTunes Store.

One account for everything Apple

We hope this information is useful. Kind regards.