A fix for the issue has been implemented and matchmaking problems have now resolved.
Jun 12, 18:53 UTC
If you are experiencing matchmaking issues on Nintendo Switch, please try logging out and logging back into the game client. We believe this will resolve the issue for most users.
Jun 12, 17:01 UTC
We're aware of issues impacting matchmaking success for Switch players and are currently investigating.
Jun 12, 16:52 UTC