Have you tried using different wands, or equipping that wand on a different character?
Is the wand broken, so Jahan is technically unarmed? Or could you have accidentally equipped a staff?
If you enable combat mode and zoom in, is the wand shown visually? What happens if you hold Ctrl and click on the ground some distance away?
Can you equip a second wand, and if so, does that get him to use ranged attacks?
Try verifying local files: in the Steam library, right click on the game and select Properties, switch to the Local Files tab and then click on the 'Verify Integrity of Game Cache...' button.
With the GOG version, in the (optional) Galaxy client, select the game in the left column, then click on the More button, and in the Manage menu select 'Verify / Repair'.