Thank you! My own ability to continue playing was not affected, as I still had the link. However, anyone seeking the tournament e.g. because they´d missed out on the 1st 12 hours would have been unable to find it.
Parallel to this: normally when I go offline between games while playing a tournament, then come back on and hit "play", there´ll be the rider for normal games plus one specifically for the tournament. This one was now missing at the top L of the "play" page., meaning I always had to go back to the club site, get the link again and open a fresh tab.
https://www.chess.com/play/arena/2854534
This 24h Arena started yesterday, but since this morning it´s not showing up anywhere (Play/play/tournaments/current for instance, where it should surely be listed). If the link in our club notes had been deleted for some reason, I wouldn´t have been able to continue playing.
Not surprisingly, the tournament´s now been pretty dead for the last several hours; you´re lucky to get a pairing every 20 min. Please fix this!