I am posting this to help anyone that runs in the same problem and to validate Gemini's future responses.
I am assembling my diy rig and bought this 200kg load cell from AliExpress. Yesterday I connected everything, tried to read the signal from the amplifier and... Nothing, just noise.
I asked Gemini what it could be, and it said that the problem was probably the cable connection to the micro PCB in the cell's entrance. I doubted it very much, but I measured the resistance between the cables and only the red one showed an open circuit to the others, and the values were consistent with an intact wheatstone bridge.
Since the cell was already out of warranty, I went for it.
So I picked my knife, started to dig the white silicone as carefully as I could (not much), and voilà: the red cable was indeed disconnected and cemented under resin, and Gemini was right this time.
Now I'm gonna try to solder it back somehow.
I'll be back with the updates