I can help you resolve the error you're having when accepting the client invitation, @ella.
Before you accept the invitation, make sure to sign out from all your QuickBooks account. Once done, try to accept the invitation.
If the error persists, try to open the invitation manually using a private web browser or an incognito window.
Follow the steps below:
- Open the invite email.
- Right-click the Accept Invitation link and copy the web address.
- Open a new private web browser.
- Right-click the address bar and paste the copied web address.
- Enter the user ID and password you use for your QuickBooks Online Accountant firm.
Here's detailed guidance on what to do if you can't accept client invites in QuickBooks Online Accountant.
From here, you can now open and review clients' QuickBooks Online or Self-Employed accounts by editing and fixing their issues.
Let me know if you need more help accepting the client's invitation. I'm always here to assist. Have a great rest of the day!