What does your doctor say? I've seen interviews with people who have this long haul covid symptom and some of them talked of some technique that basically teaches you to relearn how to taste and smell again. I haven't heard anything unfortunately about why this happens, but it is not uncommon. Covid causes a lot of long-term effects, and it hasn't been around long enough to know if any of them are permanent, but again, I have heard there are techniques that have been developed for other causes of this problem that appear to work for some. Maybe it's a rerouting of the brain connections sort of thing. Not that you need another problem in your life.