HI I had the same problem today in a trail race. 4h 27 minutes recorded but 0 nm. location services were on, app had permission and location services say app has used the location service today. ]
Phone is an iPhone 4 no sim.
came home to upload and replay and there was zero miles .
why is this?
surely not everybody has this problem?

please can we have a fix or guidance in the instructions or FAQ
thanks
Gavin