Users find it very frustrating when the performance of QuickBooks gets affected by network-related issues. When QuickBooks shows a warning message stating "QuickBooks connection has been lost," it means that there are network issues that prevent QuickBooks from connecting to a server or company data file. If you are facing this connection error, you don't need to worry because this article will highlight and illustrate all the possible troubleshooting methods to fix QuickBooks Connection has been lost error.