Apple Trade in

I traded in my iPad Pro 9,7", they say it's value is 0 euro. They say the screen doesn't respond to the touch but I know it's not true so I refused and they send it back. It's perfectly responding to the touch as before... I don't understand why they do this and I don't know how to have explanations. The support service seems to know nothing about it. It has been only a waste of time.

By the way, I had to choose a topic for this question but there isn't a topic related to Apple services like trade in. Perhaps they think it's all perfect or they know it's not at all.