QuickBooks couldn't find all of the files it needs to sync with ConnectBooks. This can happen when QuickBooks has been open a long time.
How to fix it
Restart QuickBooks.
Click File, then Update Web Services. Tick your company and click Update Selected.
If it still fails, reinstall QuickBooks and try again.
Frequently asked questions
I reinstalled and it still fails.
Contact support and we'll help.