If the clock is set correctly and the bottom oven isn't working, it points to either a faulty clock or faulty internal wiring.
As the machine is brand new, there's not a lot you can do to resolve this without invalidating the warranty.
What are the connections on the rear marked?
What terminals are the copper links across?
OK, thanks for that.
The user manual shows a diagram with 2 lives and 3 neutrals.
Are you linked for 3 neutrals or only 2?
OK, test with a multimeter that you are actually getting continuity across the 2 live connections and then the 3 neutrals.
It's not a common cause but I have come across this a couple of times.
If you have continuity (and the timer is definitely set correctly) it leaves internal wiring or a faulty timer as the cause of the fault.
Let me know what you find.
Sorry, looks like it's an internal or timer fault.
Good luck with the repair (or replacement if you go that way).
Entirely up to you whether you pay or not.
We don't gaurantee a fix, we can only advise on what the likely cause is.
If you want to open the machine up, I can advise on further checks but, as it's under warranty I would advise contacting your supplier.
As I said previously, the most likely causes (assuming it's wired up correctly and the timer is set correctly) are either a wiring fault (wire off internally) or a faulty timer.