I've recently added a Deco M5 mesh system to my house.  Prior to adding the system everything with my QNAP TS431P was working perfectly.  I could access it through the web interface, I could find it in Qfinder Pro and I could map the drives to both my wifes Windows 10 laptop and my Macbook pro and time machine was backing up.  Since installing the Deco I can only access the NAS via the web brower.  Qfinder Pro no longer finds the NAS and the mapped network drives don't work and time machine hasn't backed up.

The message below comes up through Qfinder Pro, I'm not sure how to action other than I've checked and it appears that both the NAS and deco and computer are all on the same subnet.  The NAS seems to be booted, and when I turn off the Antivirus on the Deco it makes no difference.  

I'm a novice otherwise and have no idea where to go.  Please any help would be appreciated.