Elan .mov file

I used .mov files in Elan and it worked fine the first time. Then I tried to open the same files again but it didn’t work. The warning being: No player could be created for the file/ Could not create any media player for the file / Could not realize the jmf player.
Does anybody know why this happens? considering that it worked perfectly well the first time.

This appeared to concern a Windows pc where the Quick Time Player was no longer there.