This will occur if the server QB Database Manager is not the same version as the QB Desktop.

My client is based entirely in QB 2022 Accountant.

She has a big client she accesses remotely with QB 2023 Premier.
This has run slowly, but reliable for a long time.

Her big client moved their QBW 2023 file to her Server running QB 2022 database manager.
After jumping through all the troubleshooting hoops for H202 errors, I guessed the 2022 DB manager was the root cause.

Indeed it was.

I upgraded the QB Database Manger on the Server to 2023, and multi-user mode now works correctly
I'm posting this here, in hopes Intuit tech support will add this to their comprehensive H202 troubleshooting document.