maybe you were using crystaldiskmark when the ssd was under load (windows updates or antivirus scan or game updates) maybe try running diskmark again when your ssd isnt being hit hard
Is it configured correctly? Maybe it isn't compatible with the M.2 interface (I mean maybe your SSD is AHCI or NVMe and your laptop doesn't support the one the SSD uses)
Was it second hand? If so it might have been damaged.