With the most recent Battlefield 2042 update players have been getting a Matchmaking Failed error. I started getting it myself and figured out a workaround (which was also confirmed by others using similar methods).
Error Code: 3:2907J:2903J P:84955732
Queue up for co-op solo, cancel, and then rejoin the mode you were trying to join and you will not get the error.
Quote from the Reddit post with their steps "If you get the matchmaking error, search for a game of coop/solo and wait for the countdown to start. Cancel the lobby and then try online again."
Hope this helps! It has worked for me every time.