I have been performing subcisions for over thirty years for elevating and smoothing Indented scars of all types with gratifying results. It is best reserved for deeper and wider scars, such as boxcar and rolling scars following severe acne or for chickenpox scars. That being said, there are some very important points that must be made in order to establish realistic expectations for treatment outcomes.
First, and very importantly, there is no treatment (or combination of treatments, including subcision) currently available that can realistically offer more than a 60-80 percent overall improvement in the appearance of any scar older than three months (I.e for a so-called "mature" scar). I have learned from experience that no matter how much I emphasize this fact to people before initiating treatment, their mindset hears 100percent improvement.
Secondly, to realize the 60-80 percent overall improvement can take anywhere from two to six treatment sessions (on average three to four).
Thirdly, the success of subcision depends primarily on creating a temporary blood pocket under the skin (blood contains wound healing and growth factors that stimulate new collagen synthesis, and it is this new collagen synthesis--not the breaking of the tethers--that is responsible for the improvement).
Fourth, an HA filler can be injected at the time of the subcision--not to act as a filler--but because the filler is able to stretch fiber making cells (fibroblasts) under the skin that are on the periphery of the scar, and this stretching helps them to produce more collagen in response to the blood components. (So, the filler is not acting as a filler, but as a collagen production stimulator).
So, assuming the subcision was performed properly and appropriately aggressively by an experienced, board certified cosmetic dermatologist scar treatment specialist, possible explanations for the lack of success may be that further treatment sessions were required to achieve your sixty to eighty percent improvement, and/or no filler was used to further enhance the results.
I hope this helps you to better understand and evaluate your subcision results, especially since it has proven an effective treatment over the decades with an impressive safety and efficacy record.
Hope this helps and best of luck going forward.