There are lots of stack articles citing the same error message as I am getting.
I went through the entire heroku setup doc on another computer and everything worked perf
Depending on your setup. you might have a config file in your ~/.ssh/ directory that sets which file to be used as public key to use when pushing to heruko.
example (~/.ssh/config
):
Host 127.0.0.1 #Use Heroku's IP
IdentityFile ~/.ssh/use_this_key
So if that is the case, then change the settings in the ~/.ssh/config file
Cheers