Well, add the Procfile then. This is a requirement only for Heroku.
It is also included in their sample node app: https://github.com/heroku/node-js-sample
If that doesn’t solve the issue, the last thing I could think of is disabling the cache.
I can’t say anything more without trying to deploy it myself. Goodluck!
(Edit: It’s been a while since I’ve deployed on Heroku. Last time I deployed it a year back, Profile was required. I’m not sue if it is still a requirement. Please correct me if I’m wrong.
I’m wrong here I believe, Procfile isn’t required.)