The possible cause of the error is that the invitation link is broken.
To fix the error and allow your accountant to manage the account, click the Resend invite option in the Accounting firms tab to send the invitation again. After resending, make sure your accountant accepts it immediately to avoid issues.
The accountant can also accept the invite using a different browser to narrow down the results.
Feel free to reply below if you have more questions about QuickBooks.
