Have seen it once or twice before. If there's no US tote dividends declared then all the horses have run for purse money only so BF will void the whole race.
14.8 Additional rules Where any horse(s) runs for purse money only it is deemed a non-runner for betting purposes. Should this result in the number of possible winners stated in the relevant Market Information being equal to or greater than the number of runners in the relevant Betfair market, all bets in the market will be void.
Have seen it once or twice before. If there's no US tote dividends declared then all the horses have run for purse money only so BF will void the whole race. 14.8 Additional rulesWhere any horse(s) runs for purse money only it is deemed a non-runner