why is render blank?

yes the camera is there and yes the objects can be seen when I press the 0/insert key.
yes there is plenty of light.
but hit f12 and the picture on all my recent files is blank.
and the print is tiny.

screenshot?.blend file?

screenshot of blank?
must be the video card cos after a restart of the computer - all is well

I was going to suggest you check the clipping settings. I ran into the same thing recently and discovered the scene clipping settings were too narrow…