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

Hey there,

I just finished the following the 安装iMac Intel 27" EMC 2429 双驱动器组件（机械硬盘或固态硬盘） 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