Please check that you haven’t entered your stop-loss or take-profit levels too close to the current market price or the system will not accept them.

Ensure that you haven't set your stop-loss/take-profit levels the wrong way round. Keep in mind that when setting stop-loss levels for short (sell) positions, the stop-loss must be set higher than the current market price, and take profit levels have to be set lower than the current market price.