heroku deployment fails

[djwgit]

deployed with the url
https://heroku.com/deploy?template=https://github.com/rauchg/slackin/tree/master
it worked fine 2 months ago, now, it fails with this error msg

Archive URL not found.
We couldn't find an archive URL for this repository.

with a new heroku account, new reCAPTCHA key, I think the configs are right...
could you take a quick look, probably heroku changed something for deploying from a github repo?
thanks !

[djwgit]

btw, could manually push the app into heroku, then set the config vars, it works fine.
seems something changed in heroku deployment process ?