hey hacd - here's my settings, maybe one of them will help. I'm using Midpssh 1.6.0 using the BIS T-Mobile data plan, I just connected to a server to verify it's working.
midpssh -> settings -> network
http proxy mode: off, polling I/O: off
settings -> advanced -> tcp
settings -> securuty -> TLS
TLS default: Handheld
I can't remember why I have the TLS set to 'Handheld', some app needed it that way (or maybe some website?) that I had to change it.