I have a UK spec 2015 with manual air-con, not climate control. Looking at the diagrams of
www.partsouq.com, the duct from the heater to the face level vents is a single unit, so if air is coming out of the vents at the left and right hand ends of the fascia, it must be getting blown into the duct and therefore it should come out of the centre vents, if they're open. If you shine a torch into the vent and peer through the grille, whilst you move the lever on the bottom of the vent from side to side, you should be able to see internal flap moving. On the vent to the left of the radio, the flap is hinged on the left. If you don't see any movement, it sounds like the linkage between the open/close lever is broken. If you can see the flap open but still don't get any airflow, I can only think the duct is blocked, but I can't see how that wouldn't also block the airflow to the outer vent. If the flap doesn't move, you try inserting a screwdriver with a long flat blade through the grille and try and lever the flap open. If you can open it and air now comes out, at least you'll know the duct isn't blocked.
Let's hope you don't have a snake nesting in there.
I found this video on YouTube, the first part of the job is to remove the console trim and centre vents,
How to remove a 2012-2014 Hyundai i30 Radio (#1705) - YouTube
