Thank you for bringing this to our attention, Rudolph. It's my priority to help you successfully add a new user to your QuickBooks Online (QBO) account.
I appreciate you taking the time and effort to clear your browser's cache and use different browsers/computers to invite a user to your account. To resolve the persistent error, please ensure to select a role from the dropdown menu when adding the new user. Additionally, double-check that the user you are adding does not already appear as another user type in your user list. It includes time-tracking users. Please use a unique email to invite them as a new user type.
Also, avoid using apostrophes or special characters in the user's name, as it can affect the issue.
However, if the issue continues, I recommend contacting support for further assistance. A live representative can securely review your account and investigate the error message you're getting.
On the other hand, I'm adding this article for more tips while inviting users in our system: Add, manage, or delete users in QuickBooks Online. The same reference will show you how to handle user types and permissions and delete user profiles from QuickBooks.
If you have follow-up questions while adding new users to your QBO account, let me know by leaving a comment below. I'm just a few clicks away to help. Have a good one!
