I've seen this all the time with apps and web browsers cannot connect via VPN but connections like SSH do work when connected to hot spot on my phone (also T-Mobile).? I figure it is a bandwidth issues. I know the Crestron Home craps out if there is not enough bandwidth or latency issues. I am sure the Crestron App is the same.? You might try pinging the Crestron processor and running a internet speed test via the vpn on the mobile network.? It will probably land up that both pings are slow and erratic and the bandwidth is poor.
