Here are some Troubleshoot QuickBooks error H202, to add the server computer to the Windows Hosts file, you will have to edit the file. The steps to do so are as follows:

• First, you have to open the Windows hosts file on the computer, getting the error by following either of the given paths. C:\Windows\System32\Drivers\Etc. Or C:\Windows\Syswow64\Drivers\Etc. 
• Then, click twice on the host file.
• When it prompts you with How do you want to open this file? Open with Notepad.
• Then, in the host file, add the Server’s IP address followed by the server name after the last IP address.

Note: Do not use the space key for separating the IP address and server name; instead, use the TAB key

• Now, from the File menu, select the Save button and click Exit.

After you have executed the above-mentioned steps, try to open the QB company file in multi-user mode.

More relatble error u can find while fixing it: QuickBooks error 5004  |  QBDBMgrN Not Running on This Computer