iPhone 7 iPhone not working after charger port replacement

Hi,

My iphone didnt charge lately. I bought a new charger flex and before change it I checked it connecting the flex straight to the phone and the battery logo came up.

Then I replaced the new flex and when i finished and tried to switch it on the apple logo or battery symbol didnt't come up, no response at all.

Which part could be wrong connected? I think i am going to re-install everything again but i dont have idea what could be the reason..

I would appreciate any help¡¡

Thank you in advance

I can not see something damaged like a pin or conector, do you @minho ?