Minim Server not working following Firmware update

[leighton buzzard]

Updated Firmware on my QNAP TS-221 and now Minim Server is no longer working.
Minim watch icon is grey. Clicking 'Refresh' does nothing.
If I try to log in using the IP address I get the following message, This site can’t be reached 192.168.0.18 refused to connect. If I try and open Minim Server from the App on my NAS I get the same message.
If I stop Minim Server and re-start it from the app, the Minim Watch logo goes yellow as if it's doing a rescan, I can then log in to the Minim Server Status Page, where everything looks to be ok. However, after about 20 mins the minimwatch logo goes back to grey and I can't log in again.