Hello, I recently purchased a Samsung Portable T5 SSD (500GBs) and upon plugging it into my computer It loads up a login screen that requests a password. I cannot interact with the drive and it only has 40mbs of usable space. I never set a password or got prompted with an installation setup, & the product is new considering the box was not open when I purchased it from the store.
What you are seeing the security software disk partition, the rest of the disk is hidden. It sounds like even though you bought it new, it is actually not new and someone else previously used it. The documentation says the password cannot be recovered, but if you search around, maybe this will help you:
I had the same problem with a Dell laptop. The drive was not recognized in the Thunderbolt ports. I changed the cable from a USB-C (at both ends) to a Thunderbolt cable (still looked like USB-C at both ends), but this one worked.