For accounting connector not able to connect to you QuickBooks file, users are advised to please check these settings in your QuickBooks and please send us screenshots at support@jobboxsoft.com
Go to Edit on menu and open Preferences, i.e. Edit --> Preferences
On Preferences screen, select Integrated Applications and click on Company Preferences Tab. ( Your screens might appear different based on the version you have, but should have all these settings)
On Company Preferences tab, you should be able to see ServiceBox QuickBooks Desktop Connector in Application Names list. Click on that Application Name and then click on Properties. Verify that 'Allow this application to read and modify this company file' is set. Ensure that all access levels are set as shown in these screenshots. ( Looks of the screens might be different at your end based on the version you are using)
Please try this and then try running sync again.