I have been a victim of QuickBooks error for quite sometime now. On encountering QuickBooks Error 6175, I too tried several solutions, but only these steps were useful -
Close all QuickBooks windows and files.
Hold the Windows key + R on your keyboard.
This will trigger the Run prompt box on your screen.
In the search space, type Control Panel.
Hit the OK button.
Choose the User Accounts option.
Press Manager Other Account.
Now, you need to tap on the QBDataServiceUser (your version year) button.
Go to the Change Account Type section.
Press the Change Account Type button again.
Terminate the window and access QuickBooks.
If you wish to test some other solutions, have a look here. You can also indulge in a conversation with the experts at 1-855-856-0042. Fix QuickBooks Error 6175