It appears that the stamps have been sold out.
They have been sold out/relisted/soldout/relisted/etc. I think they are closing sales periodically when they reach their working order limit.
Your right or they close shop when the post office closes down for the day. I can imagine the amount of orders that they are getting from the crypto world and the Philately world as well.
All this is good news for us Crypto heads, now that a nation has literally used a crypto loaded stamp its also gonna start others nations to follow suite. I am just waiting for the BTC stamp to come out next