I found this too. This is a match where registration is closed but has not yet started. In this case it looks like there's no start time configured, so confirm that both admins have locked. Something like this happened to many team matches in the last couple of days, and I found the API returned the match status as 'closed'
Unknown Team Match Status

I brought this problem to the attention of the developers almost two years ago & you may find this thread useful:-
https://www.chess.com/clubs/forum/view/this-is-strange
The reply from a staff member at the time was this...
Thanks @stephen_33 , the cached result for that peculiar endpoint https://api.chess.com/pub/match/993528 failed to properly refresh. Status now is on sync with Web. We will investigate further on possible causes.
But it's still very much a problem because I'm seeing typically 3 or 4 in a batch of 40 newly started matches. In a league I help to run we often have that many matches starting at the same time, so I suppose it might be a problem related to over-loaded servers perhaps?
For now all you can do is to allow for it in any code you write.

Think other than the lack of documentation this is not really an API issue.
The API is recording a status from the daily server that it doesn't understand. A match in limbo.
And, yes, I have put in a code fix to deal with it.

It has just affected every World League match that was due to start @ 17:00 UTC
All matches "closed". No games started.

"... every World League match that was due to start @ 17:00"
Ah, I have a match pending for my national team - Wales.
Same thing - no status on the webpage, just hanging it seems.

Not only WL matches are affected. TMCL960 matches are hanging already from yesterday evening. But as you said earlier, it is not API's problem. It correctly reflects the state of the art with the matches.

Think other than the lack of documentation this is not really an API issue.
The API is recording a status from the daily server that it doesn't understand. A match in limbo.
And, yes, I have put in a code fix to deal with it.
So staff are definitely aware of this problem and (presumably) dealing with it?
In this match
https://api.chess.com/pub/match/1207862
Status is shown as "closed". Not documented in specification.
Web page shows no status but match should be in registration?
https://www.chess.com/club/matches/1207862/games