Keyboard replacement

I have a Dell XPS 702X and I accidentally broke a key. It still works when I press that white membrane beneath, so it was no huge problem, but nevertheless, I ordered a keyboard on a shop some 50 kms away. I live in a remote area. When they got the keyboard from the dealer, they phoned me and I went there to change it. It didn't work. Only a couple of keys were working with the new keyboard, no more than 3 or 4. The shop assumed the keyboard was faulty and returned it to the dealer and asked for a new one. A couple of days later and the same problem exactly happened with another keyboard and... incredible as it seems, it happened also with a third keyboard, until I finally gave up and told them to forget it.

I'm still curious about why this happened. Three keyboards could not be all faulty and the third one was even tested at the dealer before being sent to the shop near me. The replacement procedure is as simple as can be and I can see why it wouldn't work...might there be some hidden configuration that they should have made when replacing it?

The old keyboard with the broken key is still here, up and running... Fortunately, it's the key with the question mark and so it's not one of those very frequently pressed... For those thinking "How on earth did she broke that key?"... well... a nasty fly around my head and a swatter landing sideways on the keyboard and missing the fly! Ouch!

Anyone has any  idea why I can't install a proper keyboars with a nice "question mark" key?