Confirmed this on the DB - it's a missing-spell issue.
The quest hands you the Horn of Echeyakee (item 10327), and using it is meant to cast its on-use spell to summon Echeyakee (NPC 3475). But that on-use spell - spell 12189 - doesn't exist in the 5.4.8 spell data at all: there's no row in spell_dbc or spelleffect_dbc for it (and the old classic spell 6021 is gone too). So the horn casts nothing and the cat never spawns.
NPC 3475 itself is fine - it even has its JUST_SUMMONED SmartAI ready - it's just never getting summoned because the horn's spell is missing.
Fix direction: give the horn a working summon again - either define spell 12189 with a SUMMON effect (Effect 28 -> creature 3475) in spell_dbc/spelleffect_dbc, or repoint item 10327's on-use spell to a valid summon (a source_type=6 SmartAI summon on an existing spell works too).