Imported .mp4 files to Rise won't play

I have imported some short .mp4 video files into Rise courses (typical file size around 35MB). I'm publishing to a 1.2 SCORM format and these are then hosted on OLM platform.

The courses playback fine to learners if accessed via laptop or using iPads connected to wifi. However, if the iPads are using 4G, the video content will not play.

Similar courses created 3 years ago are streaming without a problem on the iPads.

Any suggestions?