An error message pops up saying "Invalid Reference Id: Something you're trying to use has been made inactive. Check the fields with accounts, customers, items, vendors or employees."
This is an error message directly from the QBO, so unfortunately, we can't decode it any further. But this usually means that you are using a GL Code or Tax Code, or a Vendor that has been deleted in QBO that Float does not recognize.
The workaround here would be to re-activate the missing item (GL/Tax or Vendor) within QBO, this should fix the issue. However, if you created a new one with the same name, this would not work.