Vital Synth and Acid Pro Problem

could use some help, I purchased vital synth but I cannot get it to work right in acid pro. I use keystep midi controller, it works great for all the other soft synths and also the spitefire pianos I bought. but when I try and use vital synth, I cannot hear anything, even when I record it, although it registers input in the green midi bar when i strike the keys and also the notes are recorded but I cannot hear tham afterward. I can play the synth by clicking the mouse and keyboard on the screen, but when I record it that way i still cannot hear it. When I close acid and open the vital app, it all works fine in the vital app. does anyone know why it would be doing this? I am very new to daws, and the vital is great, I would really like to use it in acid. if not I will have to return it because I cannot use it. thank you!