First I have to say that you should give your anemone another week to acclimate to your tank before you try anything drastic.
I have saved a couple anemones from death by using a syringe to gently squirt mysis into its mouth. Sometimes anemones in ill health will lose the ability to sting or move food to their mouths, but they still need to eat. Don't try to force the mouth open and don't use chunks of food, but if the mouth is already a little open, it is OK to gently squirt some small food like mysis into its mouth.