There's a systems failure.
There's a breakdown.
I'm phoning to complain about the product.
I'm sorry to hear that. What exactly is the problem?
It's broken./It doesn't work./It's faulty.
I think I can do better than that.
What's the problem?
The problem is the photocopier isn't working.
What's wrong? What exactly is the problem?
There's some paper stuck in the machine.