QuickBooks Error 1606 typically occurs when a user is unable to access the network location during the installation or update of QuickBooks software. This issue often arises due to incorrect configuration of the Windows user settings or problems with the Windows registry. To resolve this error, it's important to ensure that the network location is accessible, user permissions are correctly configured, and the Windows registry entries are valid. Addressing these areas can help restore normal functionality to QuickBooks installations and updates.