QuickBooks connection has been lost error appears when the application loses connection with the company file while working on it. The application window will shut down, and the recently added data that has not been saved is lost. The issue may occur if the company file is corrupt or the firewall is interfering with the network connection. The issue can be resolved by restarting the QuickBooks database Server Manager in a multi-user network. If you have come across the error and you need help from a QuickBooks expert, then contact us at our (844)-932-1139.