why it wont let me add my card

What happens when you try? Error message(s)? More information would help.

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.  

See If your payment method is declined in the App Store or iTunes Store https://support.apple.com/en-us/HT203005. To resolve this, add a new payment method or update the billing information for your current payment method.

If you need additional help, use this support link from the document https://support.apple.com/contact  or use:

Apple telephone support https://getsupport.apple.com/?caller=kbase&PGF=PGF63005&category_id=SC0245&symptom_id=23362 Be patient sometimes Apple support is closed to immediate phone support.

Apple Support Twitter https://twitter.com/AppleSupport There may be an hour or so wait.

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.

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Also see: Fix ‘Your Payment Method Was Declined’ Error In App Store https://www.addictivetips.com/ios/fix-your-payment-method-was-declined-error-in-app-store/. If you need more help here, use the support links above.