Acne scars typically go through the entire thickness of the skin, and as such, tether the skin. Trying to get the tether to "release" by putting filler (any type, no matter how long it lasts) within (unlikely) or around it (more likely) simply puffs up the surrounding skin, making the scar more visible!
Subcision or excision of the scar tether is the only wayt to effectively release the attachment, and then a pearl of living fat, HA filler (short term), or Sculptra (long term, but not permanent) can fill and help protrude the scar depression.
Steroid injection can "unbundle" collagen fibers (scar) and provide improvement, but can also atrophy surrounding tissue, making a generalized depression that is another sort of problem! Not a fan (usually).
Your best treatment for acne scars is a visit to your plastic surgeon for excision/subcision and treatment of the deep or most visible scars, followed by laser resurfacing.
