The only thing I can think of is did you not "decline" the reservation? Within 24 hours you need to hit one of two buttons - accept or decline. So if after responding you did not hit decline, the system is unable to read your message - the system is only looking for either of those two inputs so it "knows" you have responded one way or the other.
For the 24 hr booking notice it is similar - you can adjust in your settings when people can book. So even if the listing says in text "24 hrs notice", you would want to adjust your booking settings to reflect that as well so guests are prevented from booking with less than 24 hrs notice.