Oops sorry, indeed there was some hidden conductive wires almost unseenable without MAX ZOOMING... And since the icon "missing ressource" didn't appear, I thought the area was fully built.
Problem solved!
Here is the BUG, I have refined metal (Copper) but the game thinks I have none.... And the ore crusher is kinda bugged too because the copper appears when it's done but disapear after 1/2 sec.