Map My Walk out of sync

Hi, yesterday I downloaded a Map My Walk app on my phone cause I had a challenge to walk 100 km in 24 hours. When I finished, I realized that I can’t see a map showing the whole track and also that it didn’t sync. When I opened unsynced trainings in settings and tried to sync it, an error appeared showing that ‘There was a problem with sending a training’.
Can someone help me? I have to verify that activity with my chief.

PS. Sorry for my English, I’m from Poland :sweat_smile:

Ah, I forgot. When I open Activities tab, that training appears after a while, but with a note ‘this training will be synced soon’ underneath. When I try to open it, a ‘loading stats’ screen appear but nothing more.