Firebase REST API INVALID_ARGUMENT on refresh-token

Question

Yesterday we started to have problems with the REST API in particular with the refresh token method: https://firebase.google.com/docs/reference/rest/auth/#section-refresh-token

curl 'https://securetoken.googleapis.com/v1/token?key=[API_KEY]' \
-H 'Content-Type: application/x-www-form-urlencoded' \
--data 'grant_type=refresh_token&refresh_token=[REFRESH_TOKEN]'

We tried this call using the curl example on the documentation and with our own development (with PHP and Guzzle) and we always get this error:

"error": {
        "code": 400,
        "message": "Request contains an invalid argument.",
        "status": "INVALID_ARGUMENT"
    }

Answer 1

It looks like this happens when you make that call from inside Google's datacentres, it works fine for us locally. It started happening to us too on the 14th. I've raised a bug with the firebase team.