A jackpot wager usually only pays out if there is only ONE unique winning ticket. If more than one winning ticket exists for a jackpot wager, the majority of the money wagered that day is paid out to winning tickets (usually 70-80%) while the remaining portion is carried over to the next time that wager is offered.
This process repeats until there is only one winning ticket (who wins the money wagered today plus the carryover) or there is a mandatory payout. A mandatory payout means the carryover must be paid out that day-along with any additional monies wagered and split amongst all winning tickets.
Each jackpot wager is governed by the host track's state regulations and may vary. You may wish to refer to the host track's website for additional information.