The service program AirPods Pro Service Program for Sound Issues - Apple Support is very clear about the problem. It refers to a small percentage of AirPods Pro manufactured before October 2020, and the service program is available for 3 years after the original sale of each device. Making a guess that Airpods manufactured in October were probably sold by December, that means the service program probably has very few remaining candidates sold between July and about December 2020.
Apple will know exactly which serial number ranges might be involved, and the dates of sale for each unit. If Apple says your AirPods don't qualify or the problem you complain about is not the target fault, then it is game over.