You might come across QuickBooks Error 6000 when you are trying to open a company file. It can trouble you because of a number of reasons. The firewall might be hindering the connection or the .tlg file is invalid.

It could also happen if the QB installation file is corrupted or there are several users who have signed into the same company file.

One way to fix it is by configuring your antivirus software by using the following steps:

·        Open the QuickBooks database manager

·        Look for the port monitor option and then the QuickBooks version

·        Note down the firewall port number and then open Windows Firewall

·        Navigate to the advanced settings and right click on ‘Inbounds’ and select ‘New Rule’

·        Click on the port, fill in the number and then click on next

This should help you to fix the QuickBooks Error code 6000.

https://www.quickbooksphonenumber.com/blog/fix-quickbooks-error-6000/