Team A starts the game with DP/Flex. Later in the game a player is ejected from the game. There are no substitutes. Team A now has nine players, but only eight batters. Does Team A continue playing, or do they forfeit?

If DP or Flex is NOT the player ejected, the ballgame is over.

Your answer is in ASA 4-D-2-a

Correct, it is a forfeit. A team may not play shorthanded when they are short due to an ejection. Batting 8 is playing shorthanded.