Specific folder permissions are required for the QBDataServiceUserXX (see below) to open company files:
Errors that occur while setting up or working in multi-user mode can be time-consuming to diagnose and correct. To help investigate and resolve the error, we recommend downloading the QuickBooks File Doctor, which analyzes whether your computer and network connection are set up properly for multi-user mode. If the tool doesn't help you resolve the error, you can return to this article and try the solutions described here.
Use the QuickBooks File Doctor
To resolve the issue manually, select the best option for your situation or perform each one in order until the issue is resolved:
Ensure the installation directories have the correct permissions. Please read the entire article before taking any steps.
Note: If running Microsoft Windows Home edition, the Security tab may not be available in Normal mode. If it is not available, restart the computer in Safe mode. (Start the computer, and then immediately press F8 several times until the Advanced Boot window opens. On the Advanced Boot Options screen, select Safe Mode, and then press Enter.)
To verify that permissions are set correctly:
Computers that have hosting multi-user access enabled but are not hosting company files can inadvertently go into Alternate Hosting mode and take ownership of a company file. When this happens, other users will not be able to open the file.