FWIW... Works for me with Safari, Chrome and Firefox on MacOS Monterey. Also tried in MS Edge on a Windows 10 VM with no problems. I don't use any extensions, adblockers, etc. however.
The message in IOS Safari is more informative: "The URL was blocked by a content blocker". I had turned off all of my extensions and restarted Safari but that was not enough. The Adguard app has to be deleted. And for some reason I got the "item can't be deleted ... in use" message even though all various browsers were closed. Once I force quit adguard it then started working.