I'm trying to deploy a simple python bot on Heroku but I get the error
couldn't find that process type 
When I try to scale the dynos. I already made a procfile and it looks like this:
web: gunicorn dep:app, where "dep" is the name of my python code  
What could be the reason?
This may happen if your procfile is misspelt, such as "procfile" or "ProcFile" etc. The file name should be "Procfile" (with a capital P).
sometimes changing the file name is not anough, because git wouldn't spot the change. I had to delete the Procfile completely, then commit the change, than add it again with the right name, and then commit that again:

remove your procfile
git commit
add a new procfile with the exact name "Procfile"
commit again
git push heroku master (or main - new heroku projects now uses main)

should work!
Couldn't find that process type, Heroku