|SeaTools detects MOST but not all hard drive brands.|
Only the Windows version of SeaTools can detect a hard drive when it's in an external enclosure.
Do the long test.
It is very COMMON for you to get a message that (the hard drive inside) an external hard drive that was working fine previously needs to be formatted if you have DAMAGED data on it due to you NOT clicking on the Safely Remove Hardware icon in your taskbar and choosing to STOP accessing the drive BEFORE unplugging it's USB connection while Windows is running.
If data on (the hard drive inside) the external drive was being detected fine previously, you need to use one of certain programs to repair the data damage.
Usually the problem is the partition table data has been damaged and because of that Windows "thinks" it has not been formatted - when you repair that usually you can then access all or most of the data on the drive again.
If partition table data has been damaged, then Windows can't successfully just format the drive.
In addition, an external hard drive may not be detected properly depending on which USB port you have it plugged into.
Troubleshooting USB device problems including for flash drives, external drives, memory cards.
See Response 1: