To be clear, you have to stay connected to the VPN on your computer in order for your files to sync with Dropbox. If you’re still having problems, one of the issues I ran into was internet speed. Sometimes with files that large, it took quite a while for my internet (which was already slow, but made slower with a VPN) to update my files.

thanks for this helpful advice, which is in line with other advice that i’ve had, and which i’ve followed.
BUT with a database of some 200GB, i find that the very large majority of my files are unavailable – either indicated with a ‘cloud’ sign, or a circle with what looks like lightning sign inside the circle.
Either way, in effect, the file is unavailable. Is there a solution..?