Problem solved. I recalled some users where having trouble with UniFi wireless access points so I reviewed the wireless settings and turned on "Multicast Enhancement" in the Advanced configuration options. Can't be sure if this fixed the issue or if the consequential wireless access point reboot but all shelly motions are now connected and showing up in the network list. This was a bit strange as I have other shelly devices on the network but just happy for the motions to be working. Cheers