How to test a replacement click wheel before assembly

I'm replacing an iPod nano 4th click wheel. The issue is when I connect the flex to logic board the iPod turns off. When disconnect it, the iPod turns on again. I have tested two click wheels and the same happen.

I'm doing this with the logic board, LCD and just only the flex of the click wheel outside the case.

Maybe i have to place every part in place since i guess something have to make contact.. I don't know, please help and I'm sorry for my english.

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