Have you checked your motion blur settings in your comp settings? There's a chance they're set to 0 (god knows why but you never know!) They're in Composition > Comp Settings > Advanced - shutter angle should be set to 180, shutter phase to -90...
What if you precomped your scene and applied a Force Motion Blur effect? Do you see any blur then?
You nailed it! Thank you!!!
I can't possibly imagine why those settings would be off, but they certainly were.
Woop! No problem
I had the same issue and your Comp settings changes fixed it!! Thanks Mr StormyCPb.