I cannot add a payment method to my Apple ID

"But the add card button is grayed out."

If an app or feature on your device is not working, not appearing, or is restricted (grayed out), it may have been disabled using Screen Time, or by an IT administrator if you are using a device owned by an employer or educational institution.

- Read this support article If your Apple ID or other options are greyed out in Settings —> If your Apple ID is greyed out in Settings - Apple Support

Tap Settings > Screen Time > Content & Privacy > scroll to Allow Changes.

- If the device is managed (Settings > General > VPN & Device Management), contact the IT department that is doing the managing.

Is your Apple Cash account restricted or locked? See this for further reference

If your Apple Cash account is restricted

Your account may be restricted if your identity verification fails multiple times, if there are multiple accounts tied to the same social security number, or if there's suspected fraud on the account. If your account is restricted, you can still transfer your Apple Cash balance to your bank or use it to make purchases with Apple Pay. You can't send or receive money, or add money to your account.

If your account is restricted and there are no instructions provided, contact Apple Support.

If your Apple Cash account is locked

Your account may be locked if there's suspected fraud on the account, or if additional security checks need to be completed. If your account is locked, you can't use Apple Cash to make purchases, send or receive money, add money to your account, or transfer money to your bank.

If your account is locked and there are no instructions provided, contact Apple Support.