The Appstore doesn't recognise my Apple ID

Log into your account in the App Store/iTunes and you should be able to change/verify it there. Or you can click the blue Edit payment methods in the article below. When signed in and the page loads, you will be on the credit card page. After updating that, click the Go Back button at the lower left and you will be on the address page.

Apple ID payment information - change.  

Apple ID has not yet been used with the iTunes store. Please review your account information

See these possibilities:

See If you see a message that says 'Your account has been disabled in the App Store and iTunes' https://support.apple.com/en-us/HT208856 "There might be a problem with the payment method that you have on file. When you see the message, don't try to edit any of your account information. Instead, contact Apple Support for help.”

Use the Apple recommended support link above first.

And, if necessary, go here is how to contact iTunes worldwide support via text or

chat using this link https://support.apple.com/choose-country-region/itunes After

choosing your country, see the heading Tell us how we can help.