3 years post-op - Neck dent and sagging (photo)

There looks to be a lot of excess skin that is sagging. The "dent" is a depression under the overhanging excess skin. If this is three years after a necklift, one wonders if the necklift was isolated or done with a facelift. It looks like it wasn't. At this point, it looks like a lower face and necklift would be needed to pull up and remove the excess neck skin. A lateral view would add some information on the degree of laxity, but the impression on the single frontal view is excess skin that would be unlikely to be sufficiently tightened by any non-invasive skin tightening modality.

I would recommend a revision face/necklift as there is significant skin/muscle laxity remaining and irregular contours.

A lower face/neck lift would make such an improvement and is easy to undergo under local with a little iv sedation for complete comfort. There is just too much loose skin for a neck lift alone.

Thank you for posting your question here!My answer will be based on the limited information and pictures provided, for a detailed and bespoke plan please consult with your plastic surgeon.
From the attached images it appears that you have an element of cobra neck deformity , this happens when the platysma muscle is no longer connected in the midline ( either it was never brought together or the sutures broke or cut through the muscle) and when too much deep fat was taken out or lost. you also have some loose skin. I am sorry that you are having those issues , but rest assured that a revision surgery will likely correct the issues in question . I would encourage you to consult with your plastic surgeon in person to discuss your options. I hope this helps, best of luck!