I'm not able to ping a wireless up-linked Unifi UAP-AC-HD device. It is marked as ISOLATED in the Unifi Controller.

Strangely the Unifi Controller is reporting it was last seen 2 minutes ago but I think this is a furphy. If anyone knows if there is a back channel that Unifi kit uses to talk over I would be interested to hear of it.

I wanted to see if there was any traffic at all being seen so I wanted to know if there was any ARP traffic coming from it so this is the command I used

 tcpdump -n -i br0 ether host 62:e8:29:bc:02:99

This is my layout

-----[ Wired UAP-AC-HD]-< wireless up-link >-[Wirelessly up-linked UAP-AC-HD]

I SSH into the Wired UAP-AC-HD and run the above command to see if there is any ARP traffic at all

Get the MAC address from the Unifi Controller by selecting the correct site => devices => select the device and from the slide out menu under overview copy the MAC Address

I ended up not seeing an broadcast traffic at all

So the device being on the other side of the world will need a power cycle.