What's the encoding difference impeding playback on iOS?
The Vegas export is 


60 fps
NTSC sized raster but with a non-square and weird pixel aspect
Audio track is first
File major brand is Sony-specific.


Many confounding factors here.

First try to rewrap

ffmpeg -i 1.mp4 -c copy -map v -map a -movflags +faststart 1new.mp4


If not, render in Vegas at 30 fps and Main profile using the Mainconcept encoder.