When using QuickBooks in multi-user mode, you may encounter QuickBooks Error 6210. When you try to access a company file on a workstation that is not set up as a server, you get a network error. QuickBooks error code 6210 means that the company file you're trying to open is not available, and then QuickBooks Desktop closes without warning. So, how do we go about fixing this problem? Don't worry. These are the steps we'll take to figure out how to fix the problem.