New NVIDIA cards are disappeared after running deep learning models

I just bought two cards, RTX 3080Ti and RTX 3060. And install them with new Ubuntu 20.04.
After installing the drivers correctly, I check the cards with nvidia-smi, and there is 2 cards.
When trying to run the deep learning models with Pytorch package on RTX 3080Ti, the card is disappeared immediately. And the number of the card detected by nvidia-smi decreases to 1.
I try to run again with RTX 3060, same thing happened. All of them are disappeared. Rebooting the system can’t get them back.
I try to re-install the Ubuntu, the cards come back, but they still disappear after the same actions. Please help.