If you get a message of “Order rejected”, this generally means that your account is in liquidation only mode or your limits have been adjusted to zero. You have either broken a rule or you are trying to trade outside of our trading hours. There will be more information available on tradertalent.com in a scrolling banner at the top of the page within 5 minutes if it is related a rule break on a purchased Tryout.
Looking on tradertalent.com - in this case where the trader tried to clip many lots (futures contracts) at once which exceeded margin requirements. They had $39,991.72  balance available and an initial margin requirement of $52,800 so they were auto-liquidated from the position and would need to purchase a reset to get a fresh account on which to be assessed: