One of my AirPods went quiet and I thought it broke so I stopped using it for a year and now suddenly they work.

Hello,

Maybe your Air Pods were low battery

I recommend reading this-

If your left or right AirPod isn't working - Apple Support

elisafromvancouver wrote:

I had tried everything, the AirPod simply wouldn’t work… But now, suddenly a full year later it suddenly works… why would that happen?

Gremlins, aliens, cosmic rays....

Seriously, that sort of problem is very hard to pin down, especially after the fact.