Cant get system working after adding SSD using the dual drive kit

Hey there,

I just finished the following the Installation d'un second disque dur (HDD ou SSD) dans l'iMac Intel 27" EMC 2429 guide on myMid 2011 27” iMac . After reassembly, I pushed the power button and . . . nothing.

Nothing is working like it does not get any power. Checked the cables and connections now three times. Everything is as in the manual.

Any ideas how I can solve this issue? Best Regards