I appreciate reporting this error message you've encountered, Jac.
This is a known issue, and our engineers have identified the source of the problem and are working to implement a solution. This can be caused by outdated versions of Microsoft Outlook. The resolution may take some time. I would suggest contacting our QuickBooks support experts to add your company to the list of affected users and receive notifications once an update is available.
Here's how:
- Click the Help menu in the upper-right-hand corner.
- Select Search and tap Contact Us.
- Enter a short description of your concern and tap Continue.
- Choose a way to connect with us. Either Start a chat or Get a callback.
As a workaround, please log into Microsoft Outlook Web from a browser and accept the invite from there, or upgrade your Outlook to the most recent version.
I'm also sharing an article on how to fix client invitations: What to do if you can't accept client invites in QuickBooks Online Accountant.
We appreciate your patience as we're working on a fix.