Hi all,
For a while now, the only way to be able to use Sampletron sounds in Sampletank 4 has been to first install Sampletank3 and convert the Sampletron sounds into an ST3 library.
Unfortunately ST3 is not compatible with the latest release of Mac OS and cannot be installed on new Macs.
Unless there is a new workaround, I'm afraid we've reached end-of-life for original Sampletron users.