I had a ulnar shortening done 2 years ago but now they said bone hasnt heal. what could be why it hasnt healed?

Healing Within Body: Surgery involves invading the body to force rapid physical changes, always inducing collateral damage, often greater than the "fix". The surgeon has no control over your control of your body & subsequent responses, though may help or hurt (easier) depending on what was done. If your internal response is that something is wrong & healing is not practical or dangerous, then healing will not occur.