Not sure what you mean by "Audio tab".
Are you referring to the Audio drop down menu?
The functions in the Audio drop down menu are contextual and will not be available unless you select some audio in your song or project.
e.g. if I drop a .wav drum loop in to Studio One and click on it, then click on the Audio menu all the functions will be available; however if I click on empty space in a song then click the Audio drop down menu all the functions will be grayed out.