When I use three-quarter flat and sharp in second intervals, it does not play.

For example, in the interval C and D, I add a three-quarter flat sign to D. The notes are written vertically (harmonically). When I press the play button, it doesn't play two sounds at the same time like an interval, it only plays one of the sounds. Likewise, when C is three-quarter sharp and D is natural, it does not play the sounds like an interval. I only hear one. But when C is a quarter tone sharp and D is flat, it plays even though the interval is the same. This error occurs only in the three-quarter flat and sharp. Why does this happen and how to solve it?