Welcome, @Alex!
Is this a booting/primary OS drive in a desktop or a laptop? I'd suggest you check your connections to the SSD and make sure it's mounted properly inside the PC. If it's a desktop, I'd also recommend swapping the SATA cable and the port where the SSD is connected to the motherboard.
If that doesn't help, you should probably
try resetting BIOS as well. This procedure will get the settings back to factory defaults, so you will need to re-configure all manual changes you have made in BIOS so far. (e.g. configuring the SSD's SATA mode to AHCI).
Give these a try and let me know how it goes. Good luck!
SuperSoph_WD