The Call timer is calculated at the desktop level. It takes the pxCreateDateTime value of the interaction and compares that to the desktop clock and determines how long it's been active. Given that the timestamps corresponds to hours since epoch, the pxCreateDateTime for the interaction is either blank or set to 0. Either that, or it doesn't exist on the page where this is being rendered. Given that the screenshot is that of a very small area, its hard to tell.