The best way to get the elf on the shelf magic back is to recharge it. You can do this by leaving it in the same spot where it was first placed for a few days, making sure that it has access to sunlight. Additionally, try cleaning it off with a dry cloth and speaking to it in a positive and encouraging voice. Finally, give it a special treat or toy to show your appreciation for its efforts. This should help to reinvigorate its magic and have it working like new again.