How to Fix Deep Nasolabial Fold?

From your description it is very difficult to give you a specific answer. If you could resubmit the post with photos I am sure you will be more satisfied with the replies. Aside from that if the fold is very deep one syringe may be insufficient. Also if the injection was placed very deep you may not see as much filling from the external view.

 

There are a couple of options for fixing deep nasolabial folds.  The first of which is to perform fascia grafts to either one or both nasolabial folds.  These are usually done at the time of a facelift since the incisions are open behind the ear and harvesting gristle or fascia can be performed and slipped into place through a small ¼” incision at the junction of the cheek and the nose.  Undermining of the nasolabial fold will also help muscular attachment to the dermis as well as the augmentation of the fascia itself.  If the fold is extremely deep, consideration for a direct excision of the actual extra fold of skin and a meticulous plastic closure of this usually heals very nicely in the nasolabial folds. A facelift procedure will not help nasolabial folds.

Without photos and other descriptions of yourself, I could not state what would work for you. For older individuals with deep nasolabial folds and weathered skin, I advocate a simple excision and plastic repair which yield as a scar no more noticeable than the natural line which runs in that area. The cost would be about that of 3 or 4  filler injection sessions and the result  would last.