Monetization Manager - App URL has already been claimed
I got the same problem. I have deleted app and with it also its Audience Network property was deleted. Now even when I have restored the app I can no longer add new property because of "App URL has already been claimed". I guess that's because that property deletion didn't release app. I've seen that this is long time not resolved issue.
Meta support: please release Android app that was assigned to application ID: 592084109274554.