If everything is up to par (as others have stated, husbandry is the first thing to check) then make sure the f/t is really warm (if you aren't already). Sometimes a heated up feeder will get them to notice it (use a hair dryer or hold next to an incandescent light bulb to get it 'extra' hot). Sometimes it works to elicit the strike. I usually also tug on the feeder once they grab it to get them to wrap it tight since sometimes they strike/grab and then drop because it's only defensive. Once they have a hold on the 'struggling' prey, they tend to go into food mode. If you can find live, you may have to resort to that to get a few meals in and then work on getting back to f/t once it's feeding regularly.
good luck!!