I had a very similar experience earlier this year with a 2020 promo code, the promo codes themselves don't expire, in fact I'm pretty sure it will still let you add the code to the shopping cart, but you won't receive the rewards as even if the code doesn't expire the stock of the promotional product in your case the key ring does, as normally the number of units is quite limited.

Ok I understand then I can try to use it in case it is still in stock?