Why my Buy Stop order rejected?


I set 4 buy stop orders through window task scheduler -run my .py file every morning at 9:31am.
I recently have noticed MRNA stop buy order has been rejected right after my run .py (the other 3 stocks doesn’t have this issue). After checking it, the same buy stop order It went through when I manually run the same one through Pycharm. So, it isn’t my code nor my computer issue. what does rejected order means? Anyone has any idea in what condition buystop order could be rejected?