Video Camera Option Not Showing Up?

[Infiniti7]

so i had my phone plugged into my computer and i went to open the camera up to record something and i couldnt see the option where you flip the button over to put it in video record mode. So i closed out and opened it back up and it was there. how come at first it wasnt there and i didnt have the option to switch it into video mode? was it because my phone is connected to the computer or what?