Export from Garmin Connect
Use the Garmin Connect website. The phone app does not always export GPX.
- Open connect.garmin.com and sign in. connect.garmin.com
- Open Activities, then the activity you want.
- Gear menu: Export to GPX. Not Export Original / FIT.
- Drop the .gpx on Travel.
FIT and TCX keep heart rate and power. Playback only needs GPS time, elevation optional. If you only have FIT, export GPX from Connect.