RealTime Sync not registering new / changed files

[manwithhabits]

Hi,
Hoping for a little bit of help please.
I have a 2016 Essentials server at home, which I use as a device to store pretty much everything - films, music and photos etc. I also have an xpenology machine.
I tested FFS recently, as a way of keeping a backup of the data in near enough realtime, to guard against accidental deletion by family. After the initial setup, I used RTS to monitor changes, which worked really well.
I uninstalled it to try another program (can't remember what now), but it wasn't as good as FFS. At the same time it broke my NAS, so I had to rebuild that.
So, I reinstalled FFS, and although I can use FFS without a problem, RTS doesn't appear to work. I used FFS (in Update mode) to copy the bulk of the data from server to NAS. Then I use the same settings in RTS to monitor the folders for any subsequent changes.
RTS loads and sits in the System Tray, and says it is monitoring the directories, but never detects any changes, even after several hours.

I'd be grateful for any help anyone might be able to give

Thanks
MWH