When I put the video on the timeline, audio works but no video?

In the Edit mode on Movie Edit Pro 16, when I preview the video it seems to work fine but when I drag it and paste it onto the timeline, the video appears to be black eventhough there's still audio playing.
Everything worked fine for the last few weeks until today :S
It's in Compatibility mode so it should be fine but no videos play properly.
HELP! Thank you!