Hi Michael,
One of the possible reasons why you have trouble logging in can sometimes be caused by a stored cache and cookies in the browser. Please ask the customer to try another browser.
Also, make sure that the bank credentials used when paying are correct. And if it still won’t go through, just process payments outside of QB payments
By adhering to the specified system requirements, you ensure quick, seamless access to your QuickBooks Online account while protecting your data and optimizing your overall experience.
For future concerns and queries, the Community Team is always here to assist you.