Whenever QuickBooks is switched to multi user mode it creates a .ND file wherever the data file (.QBW) is stored.
The .ND file manages multi user access which is usually regulated by the QuickBooks Database Server Manager (QBDSM) and(or) host computer(s). When the workstation cannot find the host IP address (made possible by the .ND file) then error messages such as -6000, 80 or H101, H202, H303 or H505 will follow.
So multiple users cannot access a QuickBooks datafile stored in dropbox.
If however you’ll be accessing QuickBooks as a single user then you may most defintely store the datafile (.QBW) in dropbox.
Just make sure you allow enough time for the updated file to upload and download on your home/ office computer.