5 months post Infini RF. Vertical lines are visible on neck and skin is now looser than before. Can this be fixed? (photos)

The problem you have is quite a common one in active cosmetic dermatology practices. I have found that the use of an appropriately robust HA filler can be injected in such a manner as to pull the skin more taut and the injection of an HA skin booster or Profhilo (where available) in a grid pattern across the central portio of the neck can work to nonsurgically achieve the kind of improvement sought here. You would be wise to consult a board certified cosmetic dermatologist and be wary of offers for the use of other so-called energy-based or light-based devices, as the hard science to promote the use of these devices, as you have found out the hard way, lags woefully behind the heavy marketing hype that surrounds these kinds of "bells and whistles." Best of luck.