Unable to save Oauth login data "request violating rules"

[tk3]

Hi. I try to use Oath to authenticate to my web app using Google.

I have successfully created login data:

for localhost and also for a custom domain that I bought. (.com)

However. When I try to create log-in data for an app that I have in Heroku subdomain (myapp-name.herokuapp.com) I get an error stating:

"Cannot save. Request was marked as violating rules, and you cannot proceed." (translated by myself, I have cloud console in my native language)

This seems to appear when I put the myapp-name.herokuapp.com either in "Authorized Javascript sources" or "Authorized URI callbacks" fields.

What could be the issue? (the error doesn't give quite a good explanation of what can be wrong)