I appreciate you for sharing a backstory of the issue, @Ianwonders.

I’m glad the H202 error you’ve encountered was resolved. Allow me to share some insights about the users’ modes in your QuickBooks Desktop (QBDT) software. 

If your company file is set to Multi-user Mode (MUM), you can set it as Single-user Mode (SUM). This way, only one user can access the file. Ensure that after using the file, the SUM should switch it back to MUM. 

To switch between modes, navigate to the File menu and select Switch to Single-user Mode/Switch to Multi-user Mode. I have here an article you can read to learn more about the users' mode in QBDT: Features available and tasks you can perform in single or multi-user mode.

In case you’d encounter the same error in the future, I got you this article that you can utilize to fix the issue: How to fix Error H202 and H505.

I’d also recommend updating your software to the latest release to avoid errors in the future. This way, we can ensure your QBDT software is equipped with the newest features and security. To guide you through the complete process, check out this article for reference: Update QuickBooks Desktop to the latest release.

You can always get back to me if there’s anything else you need help with your QBDT software. I’m only a post way from you. Take care!