Error code 9.0 when starting Raiders of the Outer Rim

Recently returned from a long time out of the game, playing on PC.

Every time I try to start this Era Battle, the game reports ErrorCode 9.0 and forces me to restart. There is no problem with my internet.

Due to my time out of the game, I only have one of the required characters (Brutus, 3-star) for this event. Is this causing the game to crash?