One of the most common reasons for getting QuickBooks error 6073 is having improper hosting configuration. For quick troubleshooting, follow the instructions given below:
Open QuickBooks on the computer where the company file is already opened.
Now click the File tab and select Utilities drop-down.
Click the Host Multi-User Access option.
Once the QuickBooks starts running in Multi-User mode, try to access the company file once again.
In case if QuickBooks error 6073 reappears while opening the company file, you must contact a certified QuickBooks Desktop expert for help. You can reach our team of certified QuickBooks Desktop experts at 1-855-856-0042.

Causes:
- The file is open on another computer in Single User mode.
- The file is located in a read-only network folder.
- The files are hosted on a Linux server and are using more than one set of login credentials to sign on to the shared folder.
- The file is being accessed using a remote software (LogMeIn, GoToMyPc, etc.) and the host computer still sees that that user is still logged on.
Solution: Manually resolve the error 6073
If the company file is open in Single User mode in another workstation
- Close QuickBooks Desktop in all computers.
- Open the company file on the Host computer.
- Go to the File menu, then select Switch to Multi-user mode.
- If are getting the same issue, reboot all workstations.
If the company file is open in Single User mode on the Host computer.
- Go to the File menu, then select Close company.
- Re-open the company file. Go to the File menu, then select Open or Restore Company.
- Select Open a company file, then Next.
- Select your company file.
- Select Open file in multi-user mode, then Open.
If your company file is located in a read-only network folder
- Go to the computer that is hosting your company file.
- Open the folder where your company file is saved.
- Right-click the folder, then select Properties.
- Go to the Security tab.
- Select the user that is having issues to log in, then Edit.
- Check Allow for Full control.
- Select Apply, then OK.
Regards,
Peter
Go to the Security tab. Select the user that is having issues to log in, then Edit. Check Allow for Full control. Select Apply, then OK.
...
If the company file is open in Single User mode on the Host computer.
Go to the File menu, then select Close company.
Re-open the company file. ...
Select Open a company file, then Next.