I have enough NESO in my inventory but can't enhance my item.

If you have sufficient NESO in your inventory but can't proceed with enhancement, it is likely that you are currently holding NESOLET instead of NESO.

You need to convert NESOLET to NESO to use it for enhancement.

In MapleStory N, the currency used for game content is NESO. 

To convert NESOLET to NESO:

1. Obtain NESOLET through gameplay.
2. Claim NESO from NESOLET in your character inventory.