It's concerning when the issue has been recurring for an extended period, @DMD6. I'll point you in the right direction to resolve the error prompt received by your users in QuickBooks Desktop (QBDT).

Since the issue persists after performing the suggested troubleshooting, I recommend reaching out to our customer support team. This way, they can look into this further and walk you through the resolution. They can also initiate an investigation if need be.

To do that:

Go to the Help menu and click QuickBooks Help.
Select Contact Us.
Provide a brief description of your concern, and click Continue.
Log in to your Intuit account, select Continue, then Continue with my account.
Enter the single-use code you received in your email and hit Continue.
Choose between Chat with us or Have us call you.

Furthermore, you can refer to this article to manage your users in QBDT: Create and manage users and roles in QuickBooks Desktop Enterprise.

You can ask us anytime whenever you have further concerns regarding user permissions. We'll always be available to help you out. Stay safe.