I bought an armor buff from the mage but, altough she casted, it had no effect on me. Also you cannot ask the trader to be shipped anywhere altough he offers the option.
I have seen this on other NPC priests, it happens with the Helmite if you click thru the dialogues too quickly, and often happened in some of the Lairs Priests, regardless of click thru, specifically the Nercomancer Lair, the same spell, Mage armor, constantly had this issue. It finally got resolved. This sounds similar, tho.
Just checked this, the spell is cast, coin deducted, but 0 effect to AC for Mage Armor. Nothing to do with click thru speed. The AC boost on cloth simply is not applied, though the VFX is. And, strangely the icon for AC increase is as well. But no AC change.
Is it mage armour? I thought it was magic vestment?