I am unable to add new credit card to pay subscription which has been suspended All I get is a blank grey screen.

Hi iain-mckechniema, thanks for joining the Community

Please confirm that the address for the credit card matches the address in your QuickBooks settings. The addresses must match to authorise the payment. You can check the address by logging into your Intuit account > navigate to the Profile tab > Address. 

If you're still unable to re-subscribe following this, please contact our Live Support team so we can check some additional information. For more details on how to reach them, click this link: How to get help with QuickBooks.