So you get into the ring, and they won't fight you. You attempt dialogue, challenge them to a fight again, and the game reloads the ring and the fight begins.
You defeat him and then you're stuck in the ring.

Whiskey tango foxtrot? If this ever happens to you, load your last save before the ring, get into a random encounter, watch the aggro behave as anomalously. Fight to the finish, then head back to San Fran. The dialogue and fights should act as normal.

It just needed to get it out of its system, I guess.