I am facing the same issue here, I have tried 2 different WIFI and 4g network but it still does not work. The home wifi only has 1 connection when i tried. Funny thing is that the friends will show up on the Invite list, which means they are already fb friends, but yet DML friends list is not showing up correctly. Anyone also facing the same issue pls let us know as well.
Also tried connecting, disconnecting fb in DML, unfriend and friend again, invite again. I am running on vpn, hope this is not the cause.