no video

During my zoom meeting yesterday, the video did not work.  Only my picture was available.  In the bottom left corner, the video indicator had a red slash through it.  So I clicked on the up arrow, and I saw that the camera on my pc was selected....as there are no other cameras.  But when I clicked it, I got a little box in the upper right hand that told me to select another camera.  Again, there are no other cameras. Can someone help me with this?