There may be three reasons why your order was rejected.
1. There was insufficient margin (Please note, that while taking a position, the amount of required fund is displayed on the order card. Please ensure that you have that balance before placing the order to avoid rejection.)
2. The stock you are trying to buy has already hit the day's circuit. You can check the day's circuit (low and high range) on the order card.
3. As per Groww's RMS policy, you cannot take fresh positions after 9:15 AM on the expiry day of the stock option.