PC does not boot after transport and cold night in the car

My brother wants to give our grandma his old dekstop PC, since he recently got a laptop. He installed a new SSD, installed and set up Windows, and loaded the PC into the car. Until then everything went smoothly. When we arrived for Christmas we initially forgot the PC in the car. That might have been our mistake because it was only just above 0 degrees that night. When we brought the PC into the house the next day, a lot of condensation formed. We therefore let the PC dry for a day. However, the mainboard battery was still in the device. The next day we connected the dry PC and tried to boot it. Without success. The PC does not show any signs of life. No fans, no beeping, no LEDs. In the meantime, we disassembled and reassembled everything, hoping that only one connector had come loose. Which was apparently not the case. We are now back home and have successfully tested the RAM in another computer, bypassed the on/off switch, and installed a new BIOS battery. Still nothing happens. Where could the error lie?

Edit: We just used another power supply. Still without success.