Thanks for informing us :)!
But i still got some open questions about this:

Is @wochenblick the one reported on or was there another account?
I could not find ANY other examples this happened.

Are you absolutely sure, that no one could have flipped a switch in any way, that has caused this problem somehow on different API´s? The timing this happened (including some taken actions) is more than giving this a fishy smell?
And if so, just this one account??

The problem seems to be solved now, your API is also back working fine with this one example i can to do tests on. @pharesim ´s API is not working at all and @roelandp ´s is producing errors, but at all: any information for the public about what caused this problem? Different versions, old "blacklist implementation" on old versions running or what ever? I can´t think of a misscalculation causing this for just some API´s without running different versions or something to be honest?
https://beacon.peakd.com/ is sadly not showing any versions api´s are running.

Would be very nice to get detailed input on what exactly caused this problem as soon as it´s clear, cause i might have to say sorry for some things ;).