I'll share additional troubleshooting steps, Leahkershner1103 and John_K.

To answer the question is yes, QB 2020 co-exist with other versions on the same server and support multi-user mode.

QuickBooks Database Server Manager allows sharing the company files with other computers on a server. May I know if you install the server only or the full program option? Any information will help me identify the best course of action for resolving multi-user mode issues.

On the server PC, the full program option refers to installing the full version of QuickBooks Desktop and the Database Server Manager. Since you host different versions of QuickBooks Desktop on your server, you'll have to install them from the oldest version first and up to the most recent. For each version of Database Server Manager, QuickBooks creates a new Windows user. For example, Data Server Manager 2019 shows up as QBDataServiceUser29.

As I've stated above, folder permission is one of a few reasons why the multi-user mode doesn't work. If folder permission is set up correctly, let's configure each Database Server Manager. I'll show you how.

1. Open the Windows Start menu.
2. Type “Services” into the search and open Services.
3. Select and open QuickBooksDBXX (XX is the version number).
4. Go to the General tab and find the Service status section. If it's Started or Running, click Stop.
5. From the Startup type dropdown menu, select Automatic.
6. Go to the Logon tab. Select the Local System account option.
7. Click the Recovery tab. choose Restart the Service from each of these dropdown menus: First failure, Second failure, and Subsequent failures.
8. Go back to the General tab. Hit Start to restart Database Server Manager.

If the issue persists, continue with the rest of the steps in this article: Install QuickBooks Database Server Manager.

I've also added this resource in case you've encountered errors H202 or H505: How to fix Error H202 and H505.

I'm only a few clicks away if you need further assistance with multi-user mode. It's always my pleasure to help you out again.