I can’t add a card after removing a card

Sign in to your Apple ID account page and edit / update your Apple ID details.

https://appleid.apple.com

On the Sidebar click Payment methods -> then tap Payments Methods and tap Manage payment method.

See also -> Change, add or remove Apple ID payment methods

Change, add or remove Apple ID payment methods – Apple Support (UK)

See the following Apple articles:

Set up Apple Pay

Set up Apple Pay - Apple Support

Set up Apple Pay in Wallet on iPhone

Set up Apple Pay in Wallet on iPhone – Apple Support (UK)

If you can't remove a payment method from your Apple ID

If you can't remove a payment method from your Apple ID - Apple Support