Account number or card number requires an industry standard 16 digit number. Do not use anything other than numbers, no spaces, no hyphens etc. Expiration date may be in two formats, MM/YY or MM/YYYY. If it doesn’t accept a 2 digit number for year of expiration, it may need a 4 digit number. Lastly, you’ll need to enter the 3 or 4 digit security code, often referred to as CVV or CVC etc.
Please take a screenshot of the error message, so that we have the exact verbiage. Post the screenshot and block out any personal or account information. You may also want to contact the bank and ask if they even see the attempt to add the card. The bank has to verify the data and confirm the account is active etc.