Within Settings->Display there is an option to choose your trail
display and also how many points to store. The default is 150 and only
show end of trail. Therefore you see only last 5 minutes (time is
relative to your speed, at a 60kmph car drive my trail time is about
3m 45s).
150 works stable on most phones. You can play with this setting. At
times a high number say 1500 will show a very long trail but MTE will
struggle to save it when you choose to stop it. For such cases, make
sure you activate stream recording also from settings. Streams saves
the trail in realtime and therefore you will still have a backup if
MTE could not save the GPX/KML file.