I've had the same problem with one of my pastels. I switched her to live and didn't have that problem anymore. This is just my opinion, but with my pastel girl, it seems like maybe she constricted the f/t so long, it got cold so she didn't eat it. Maybe try to heat up your f/t with a blow dryer, especially the head and see what happens...

Either way, live or f/t, definitely try all other options before force feeding. That should be your absolute last option.