Surface Laptop 3 won't turn on or charge after battery replacement

My Surface Laptop 3 battery was lasting less than an hour so I decided to replace it myself, pretty sure it was easy and straightforward because I remember that the SSD i replaced like 4 years ago was very easy to serve.

I ordered the battery and put myself to work, using the iFixit guide step by step. After reassembling everything, the laptop would only work when connected to the AC: the light on the charger was on but windows would not see any battery and it would istantly turn off as soon as I disconnected it from the network.

Suspecting that the battery was not correctly connected, i disassembled and reassembled everything again, but now it wouldn't even turn on and the light on the Surface Connect charger wasn't showing. After disassembling and reassembling everything again, I convinced myself battery was fauly and bought another.

I have installed the second battery but I have still the same problem: laptop won't turn on and "charger won't charge" (meaning no white led on Surface charger).

I suspect I may have made some damage to the internal circuitry and am just about to give up and accept the fact I will have to buy a new laptop, but I am here asking if there is anything I can try before finally giving up. I have followed the guide very thoroughly, especially last time, so I wouldn't suspect any missing connectors or something like that, but would like to hear others opinion on any common mistake one could make when reassembling this model which could be related.

Any help would be very appreciated.