Heroku deployment error H10 (App crashed)

$heroku run rails console 

This is the best option since it will give you an error in your terminal which will be much more detailed than the 'app crashed' error in your Heroku logs.

I ran into the same error above, app was crashing on heroku (running fine in dev) but error logs on heroku were not revealing any clues. I read other answers on this page and broke out in a sweat after seeing "rebuilding the app." I figured maybe I could get in the heroku console and look around. I did and even the console crashed, but this time it told me why. It was some obscure variable I forgot to delete during a troubleshooting session hours earlier. I am not saying you will run into the same problem, but I found more info when I tried to go through the console. Hope this helps.

$ heroku run rails console

$ heroku restart

helped me get my dyno running again. I'm new to Heroku but glad I know now.

I was having the same issue. Logs weren't giving me any clues either. So I scaled down and scaled back up the dynos. This solved the problem for me:

heroku ps:scale web=0

Waited a few seconds...

heroku ps:scale web=1