Moderator’s Note
I’m tracking this as a potentially separate issue from [SOLVED] Matchmaking still running after 19 hours / no War matchup weekend of February 6, 2021, but it may turn out they’re related.
If anyone else is experiencing this same specific issue of being stuck in Spectator Mode, please report it here, and also contact-support to submit a ticket from within the game app.
Thanks!
EDIT: thanks to @Sarah2 for pointing out this appears to be a reoccurrence of a previously-reported issue: [SOLVED V34] Returned before war started, but Ex-member on the battlefield? Help!