Thanks for taking the time to reach out to us here, userhobartcrest.
Your customer will get this message if there a problem with the account that is linked to your payments.
To remotely check your settings and reset the link for the Review and Pay button, I recommend reaching out to our Merchant Service Team.
You can get the contact information here: Contact Payments Support.
I'm just a post away if you have other concerns with QuickBooks Online.