Can't edit credits callback url in Facebook Application
I try to edit credits callback url in Facebook Application Edit page. and got
Unable to update Test App settings, please verify that all of the test apps are valid.
and no more information.
This is a known problem which seems to be introduced just yesterday, see https://www.facebook.com/help/community/question/?id=2166100
I imagine that facebook will react to it soon.
Edit: Just to give an update, there are two relating bug reports:
Edit2: Fixed for me now!