I have also seen that this happens occasionally in recent versions. I have not located the problem, but if you press RUN a couple of times in the package center on domoticz, it tends to start. It also usually starts immediately after a reboot of the NAS.
If you use Python plugin, it can be a ...

NEW! Domoticz Beta version 2020.2 for synology uploaded for testing.

http://www.jadahl.com


@jumbotroll
I upgraded from 2020.1.11835-8 to 2020.2.12213-8 (cedarview version, DS412+) and domoticz hangs / stops after the start. I had to go back to 2020.1


I have also seen that this happens ...