basically title. when playing guardian I can only transmog my weapon to the default claws of ursoc appearance. Right clicking the weapon in the transmog screen to “transmogrify as” changes nothing.
Do you have an enchant appearance on it?
I just tested on my Druid … she equipped an heirloom polearm.
At first I was not able to get any Guardian Artifact appearance to take. Then I removed ALL her gear except for the weapon and was finally able to apply a Guardian Artifact appearance to it.