There is an error in the log similar to this:
There is only one cause: QuickBooks is not open in Multi-User mode. You would receive this error message when trying to synch QuickBooks Enterprise files, and not when using QuickBooks Pro and Premier.
You would also only receive this message if QuickBooks is already open in single-user mode, or if somebody else on the network is logged into QuickBooks in Single User mode (which is necessary for certain Admin functions in QB).
Make sure that QuickBooks is in multi-user mode, and ensuring that it CAN be in multi-user mode. When our recommended instructions for leaving QB open to NO company in a multi-user installation are followed, QQube will auto-login as multi-user mode.
For a single-user installation, typically a user has QB open already - just ensure it is in multi-user mode before starting the synch process.
is requesting access to a wiki that you have locked: https://clearify.com/wiki/view/4142/enterprise-multi-user-mode