Since 1.21.2 recipes in data packs cannot be loaded, including recipe for all kinds of work blocks such as crafting table, furnace, stonecutter etc. I am a data pack developer, my data pack works all right in 1.21.1. I've searched the update log on the Minecraft wiki, but it doesn't mention any changes in recipe of data pack.
Here is my data pack, you can have a test in 1.21.1 version and the newest release and snapshot/prerelease/candidate version to compare the differences.
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The format DID change. Compare your recipes to the vanilla recipe files.
Wiki lists it just fine here: https://minecraft.wiki/w/Java_Edition_1.21.2#Data_packs_3