Permission denied to `heroku fork` app but able to push code to same app

Permission denied to `heroku fork` app but able to push code to same app

I am able to execute something like git push heroku master with no
problems but when I execute heroku fork -a heroku staging (where heroku is
my existing app and staging is a new app I am trying to create) I get ' !
You do not have access to the app heroku.' and the fork does not initiate.
I am following the instructions at
https://devcenter.heroku.com/articles/fork-app
I am trying to just make a staging environment and would like to use fork
so I don't have to manually copy over config vars or DB data. Thanks.