I lost my ability to smell 8 years ago. i have been to ent specialists, had allergy tests done and even gone for a cat scan. i don't have any allergies and thankfully, nothing abnormal from the scan. what else could be causing this? how can i fix it?

After viral infectio: Many different causes. Likely a complication of a viral infection that caused loss of nerve of olfaction function. Was there a history of severe nose / sinus infections or meningitis ? Any major head trauma with fractures at the skull base ? Rarely it could also be an early sign of neuro degenerative disorders like Parkinson diseases.