Android 5.1 device won't join LAN session while Lollipop 7 devices do

I have a PC creating a LAN session, opening the level, and spawning as a spectator. While Android devices join the session and spawn as playable pawns.

My Nexus 6P running 7.1.2 can join the session as well as a Shield running 7.0, I have built these as ASTC.

But a MotoX running 5.1 can not join the session, when I click on the join button the menu should collapse on success but it doesnt, and on the PC I can see that no client connects. This APK was built as ATC for the Adreno.

Any ideas of how to troubleshoot the networking of this 5.1 device? I can also click ‘host’ and it will create and spawn in a new session. I just can’t get it to join the existing.

UE 4.16.3