The Game Data Endpoint for Spells returns 404 for every azerite spell power in any Azerite item.
Some examples:
/data/wow/spell/280013?namespace=static-8.3.0_32861-eu
/data/wow/spell/263978?namespace=static-8.3.0_32861-eu
/data/wow/spell/279778?namespace=static-8.3.0_32861-eu
It seems its not just azerite spell powers. Lots of other base spells return 404 as well. Spells from talents and pvp talents seem to work but not base spells for a given class.
For example
/data/wow/spell/255937?namespace=static-us&locale=en_US (Wake of the ashes) works
but
/data/wow/spell/20271?namespace=static-us&locale=en_US (Judgment) does not. Returns a 404/BLZWEBAPI00000404
Similarly for other classes as well. Tried warrior spells, talents/pvptalents seem to work but base spells return 404 responses.
As noted in the previous post, all azerite spell powers also return 404.