Difficulty opening your company file can cause the QuickBooks connection has been lost error. For this, QB must be closed immediately, or any unsaved data will need to be re-entered. You can eliminate this error by restarting QuickBooks or running the Quick Fix my program from the QuickBooks Tools Hub. For further details on this issue, you can also refer to our article on the very same. If the error persists, you can reach us at 1-855-856-0042 to get immediate assistance from our support team.