Unknown block tag

ive tried to solve this myself, but have come up short with all online research.
im trying to make myself a block tag "apsys:non_solid" that contains most blocks with small/non-existant hitboxes, but whenever i attempt to use said block tag i get the same 'unknown block tag' message as usual. i created the block tag with https://misode.github.io/tags/block/ for my version (1.21.7), and the datapack its contained in works with multiple functions ive made for it already. id love if someone could point out the mistakes ive made, assuming they exist. im simply just very confused.