Thanks for taking the time to visit the Community today, Eight.

I'm here to help you log in successfully to your QuickBooks Online Plus account.

There is a possibility that the user invitation was not acknowledged reason why you're getting the error. Sometimes the invitation emails can get sorted into the spam folder. If this is the case, please ask the new user to check their spam folder and make sure the invite isn't hiding out there.

If the email is not found in the spam folder, you may want to try resending the email. Here's an article for more information on what to do if the person you invited didn't receive their email: What to do if invited users did not receive your email invitation.

For additional troubleshooting options, you can refer to the steps provided in this article: Get help if you can't sign in to your account.

With this information, you'll be able to get the new user added. Keep up the great work and let me know if you have any other questions.