I had a this problem –
When he’s finished a route tell him to ‘convert all to trail and reset’ rather than just ‘convert to trail’.
Then plug it into computer and load up the SatSync software – should then see a few files, one is a .gpx – upload that one to Strava (There may be a couple of gpx files, try them all).
Even though the ‘convert to trail’ option creates a .gpx it doesn’t seem to have all the info in it and therefore important to select ‘convert all to trail and reset’.
Let me know if that works – I was never sure if it was just mine that a bit awkward or if they all worked like this.