Question about WD Black SN850X powered by SANDISK

Hello all, I have the problem that the SSD is no longer recognised after a reboot. It is also no longer displayed in the Bios. on/off of the card does not work (LED of the card does not light up). If I then remove the card in the Bios while the PC is running and install it again, the card is active (LED lights up) and is recognised. The next time I restart the computer, the same problem occurs again. Does anyone have a solution to this? What I have already done: - reinstalled the operating system (Windows 10) - All drivers are up to date Mainboard: Model: X99-DELUXE II Chipset: Intel X99 PC: https://www.digitec.ch/de/s1/product/digitec-zenon-z5000-intel-core-i7-6800k-32-gb-256-gb-ssd-hdd-pc-5807230?supplier=406802