Ive just done 60 mins of a longer workout using the app on my android phone as ive done on many occasions. I had to cut the workout short as ive ran out of time. The app has been showing this spinner for the last 10 mins and wont change. I dont want to close it down and lose my workout.
My experience. You shouldn’t lose it. In fact, you can go to another device and it should ask you if you want to continue your workout. But I believe it only picks back up within a few minutes? I have had it crash. Stopped to get a kid. Came back and it asked if I wanted to complete my workout.
I faced same issue 2 times already. Luckily I double recording with my Garmin watch. Resume workout didn’t work in my case or maybe partially 
. It restored workout from 1h05min where it was 2h ride at ~0.9IF, so you can imagine that it was not an option to redo last h.
In 2nd case I just waited 5 min. Checked TR calendar on website and it showed completed workout, then I have shot down PC app.