Hi there, you can connect your SSD to a computer to see if it shows up there. If doesn't, then your SSD is problematic, you should contact the manufacturer for an answer. If it shows up on your computer, then go to Disk Utility to see what it is formatted. If it is formatted to non-Apple file system, like Mac OS (Journaled) and APFS, you should format it to Apple file system first.
Read to know how to format an external hard drive on Mac.