QuickBooks error 6123 is caused when a user is trying to restore the backup of the company file from the hard disc drive or when the file is being opened via multi-network server. The error message QuickBooks error 6123.0 gets displayed on the screen. This snag can be resolved by applying some alternative methods. It is recommended that you try to implement all of them, and then get in touch with the techies at Quickbooks Technical Support.
Download and install QuickBooks File doctor in the system to scan for the errors and then fix it accordingly.
You can rename the .ND and .TLG file
Try moving the company file from one location to another
Installing the QuickBooks software again can also help.
You can also create a new user for your system.
Call for assistance
Quickbooks Customer service phone number