Let's do the basic browser troubleshooting steps and see if this is just triggered by a full cache. A cache stores your browsing history, but it could cause unusual behavior in QuickBooks when it's full.
When your invited user clicks the invitation link from the email, they can copy the URL to a private browser.
Google Chrome: Ctrl + Shift + N
Mozilla Firefox: Ctrl + Shift + P
Internet Explorer: Ctrl + Shift + P
Safari: Command + Shift + N
Private browsing stops the cache from saving their browsing history, and it's a good initial step to check browser issues. If they can successfully accept the invitation, they can go back to their regular browser and clear its cache. If it's still the same thing, they can use other browsers to isolate the case.
Mozilla Firefox.Note:To preview and print forms on Mac OS, you'll also need the Firefox PDF plugin.
Safari 11 or newer (Mac only).
If they still can't accept the invitation after trying all steps, please contact our Support to check this further.
Click on Help and choose Contact Us at the bottom.
Enter a summary of the scenario and click Let's talk.
Select Chat or Email us.
Let us know when you still need help adding users to your QBO company.