QuickBooks Error 6123 arises when the user is trying to restore the backup of their company file from the hard disk. It can also occur when you are trying to open the company file from the multi-network server. You can resolve this issue by following the below-mentioned troubleshooting steps:
Δ After installing the QuickBooks File Doctor, try to repair the existing version of the file.
Δ You can even give a new name to .ND and .TLG file.
Δ You have the option to move the company file to a different location.
Δ By using the Auto Data Recovery Feature too, you can fix the error code.
Δ Disable the installed antivirus software of your system.
Even after executing these steps, if the error is not fixed, then you have to give a call to QuickBooks Support and speak with the experts for the solution.