gigabyte rtx 3060

Hi guys! Please help me solving this mystery I have two graphic cards of the same model. GPU1 is not detected by my previous motherboard (MB1) and my current motherboard (MB2) but working fine on other PCs. GPU2 is working flawlessly with my current motherboard (MB2) GPU1 : Gigabyte RTX 3060...

While playing a game, first the screen suddenly freezes and after 2-3 seconds the monitors go off. 4-5 seconds of sound etc. It continues, then the DRAM and VGA lights on the motherboard blink and the computer restarts itself. The computer is considered newly assembled. Everything is up to date...

It worked flawlessly until it was opened to replace the thermal paste. After changing the paste, the card does not work. The fans are spinning, the RGB led lights are on, but the indicator on the bottom shows a GPU error.There is no visible damage to the crystal or any element of the circuit...