They just added cloud saves to this game last month, so if you changed computers before then, that would explain it. If you still have access to the files from the old computer, you could copy them manually. Or, if you still have access to the old computer, you could potentially update the game on the old computer (to get the cloud save feature) and run it there, to get your save in the cloud, which should then be d/l'ed to the new computer.

If you don't have access to the old files/computer, then I think you're just out of luck.