Smoke a bong, eat ice cream.

You'll taste something.

Edit: It's a psychosomatic block. The nerve functions associated with taste and smell are being cognitively blocked off by conscious attention. It's like trying to get a name that's on the tip of your tongue but you just can't seem to find it. It's not that you don't know it, but the brain is blocking it off.

Same here. It's not that you can't taste or smell, just that your brain is blocking it off. If you can just shift your assumptions and reset the brain, weather via meditation, exercise, breathwork or something else, it will bring back your smell and taste. But it might go away again if your underlying assumptions are not sorted.