It might be useful for the developers if you send a debug log (from About) right after you are successful in getting UPnP to see the MMW server after first failing. Then respond with the logID.

Got it. Had a friend come over and we literally just sat and clicked UPnP on the phone over and over and over until the server decided to show up. Same thing with his phone. Super glitchy here. Any idea why it would struggle like that?

I've just downloaded MMW on a W10 computer and MMA on my Samsung S8 and Pixel XL 2. After tinkering with every setting I could find, the S8 seemingly randomly decided to start seeing the the MMW server on both UPNP and Sync. However, the Pixel XL 2 just won't see either.

The firewall on the MMW is turned off, though the S8 works fine with it turned on - I have followed all known instructions for forwarding ports and giving apps and services permissions. A different W10 computer can see and access the MMW server on the network. I've already plugged the Pixel 2 XL into USB and it shows up in the "Portable Device Sync" settings. In those settings I have checked the "Grant remote sync..." option. I just can't get the Pixel 2 XL to find server over wifi. Again, S8 works fine. I've reset all devices multiple times.

Any ideas?