Before proceeding with the troubleshooting steps to get rid of QuickBooks Error 6129, you must keep the following things in mind. This is so that you can easily fix the error without facing any issues. 

1. Always use the updated and latest version of the QB accounting application. 

2. Reboot your system and then try to sign in with an admin account on Windows. 

3. Access the sample data file to verify whether the issue is with a specific company file or with every data file. 

4. Try to modify the name of the data file if you are still getting the issue. 

If you have any query regarding QuickBooks Error 6129, don't worry and take assistance from the experts by dialing the contact number +1(855)-738-0359.