Firefly will not generate video for images that seem racy.

Hello,

I'm having issues with Firefly generating images( black and white sketeches) to video. It gets about 1/2 way and then stops and says We can't process this prompt because the reference image
doesn't meet our User Guidelines. You can upload another
image and try again." Can anyone at least tell me why and if I can't do this what program will?