I have one of these units installed indoors. It's worked fine using LAN backhaul and AC power.  

I just moved it to a different location and bought a TP Link PoE switch to use it with PoE.

TP-Link PoE Switch 8-Port Gigabit - TL-SG1008P

4 PoE+ Ports up to 30 W For Each PoE Port and 64 W For All PoE Ports

When I powered it back up the light was solid green, but the unit wasn't showing as connected to my mesh in the Deco app

I checked the switch to ensure there is both power and link. See below port 2 showing full power and 1000Mbps

Next I removed the X50 from my Deco app network, then unplugged the ethernet cable and plugged back in to reboot the device.

This resulted in yellow (booting), then flashing red (disconnected), then finally Solid Green again... but it's still nowhere to be seen in my network!