If no video is visable, check the frames per second indicator on the status box. It should give a value fluctuating around fps=25.0 (PAL European system) or fps=30.0 (NTSC US system).
The video input is connected to the right input. For the ImagenationPX610, there are two BNC connectors. The lowest BNC is a trigger input, the top BNC (closest to the multipin 'D' connector) is the video input.
The video source has been switched on. i.e. the IPS Isolator/Power supply (mains switch is on rear panel) and VCR.
If using an LCD monitor, check the brightness and contrast settings. Sometimes the low contrast when out of focus just gives the impression of no video signal.