Sounds weird. Maybe try pushing a different branch would do?
git branch production
git checkout production
#do some code changes
git commit -am "some desperate code changes to try fix heroku"
git push heroku production:master
Creating a new production branch is what I want you to test. Besides, it’s nice to have a production branch that you can use to deploy.
If it doesn’t work, then I think the problem runs deeper and you need help from heroku.
EDIT:
Add the heroku releases addon too. Rolling back is as easy as heroku rollback