When will I be able to move my eyebrows after endoscopic brow lift? It's been three weeks, and my face is frozen.

Forehead movement is usually reduced after a brow lift due to postoperative swelling.  However most of the swelling should be resolved by three weeks. This suggests that weakness of the frontal branch of the facial nerve could be the cause of this reduced forehead movement.  Stretching or manipulation of this nerve during surgery can cause a temporary weakness of this nerve leading to reduced forehead movement.  Usually this will resolve on its own within 3 months but can at times take up to 6 months or even a year to resolve.

but on the assumption that you do have some kind of injury, all you can do at this point is wait and hope that the nerves will recover and movement slowly returns.  Nerves are usually stretched during this procedure so chances are good things will turn out fine.  If you even have twitches, that is an encouraging sign.  But you should get the definitive answer from your surgeon since he/she knows what was done and if there were any difficulties encountered.