how to wipe clean a previously used SSD?

[MiddlemanOne]

The reason it's not being recognised by Windows is because its likely to be formatted as a Linux drive under the Synology OS, possibly as EXT3 or EXT4 formats and possibly encrypted. It's a similar issue I have experienced with Zyxel's drive, which has their own proprietary format for their NAS servers, which makes it very hard for them to be cloned should issues arise even with a standalone drive cloning dock. But it could also be your SSD could be in need of a firmware upgrade or maybe is not compatible with some drive dock electronics. Some cheaper SSDs apparently can never be used properly as normal HDD replacements (even with cloning) because they have a limited amount of cache headroom.

[MiddlemanOne]

Well you were fortunate your SSD was able to be recognised by the GParted software. I've had cases where I've placed a used 256GB M.2 SSD into a small USB case to be formatted, only for the drive to fail rendering it totally useless because of some quirk in the setup. I'm not sure what the issue around the GParted non-reading of the drive is, but it sounds like its possible something akin to what we get when you have two of the same named volumes in a Windows PC which are direct copies of each other - only one ever appears on the desktop despite the 2nd being fully connected and working.

Despite their supposed successes, SSDs are still likely to fail like any other electronic product. I've had more than a handful of SSDs fail (mainly 128GB types) because the drive just wasn't up to scratch when it came to proper usage (poor error correction in the electronics). If you want reliability, my go-to brand for SSDs is definitely Samsung.