In the app, go to "Climate", then press the button, with wavy lines, at the bottom, on the right hand side to select "HI", it should thaw the charge port fairly rapidly. Might also work on the door latch. See page (12 of 193) in the manual or just search for "THAW"
Ah, that's useful ... I didn't notice that in the manual before ... my first winter with the M3.