I downloaded the TTS1 recently from Bandlab.
It comes with Bandlab Cakewalk as a free download.
There is a download button on the main page https://www.bandlab.com/products/cakewalk
That will install the bandlab assistant. One has to register an account in Bandlab.
From the bandlab assistant one need to login and from there one can download Cakewalk which includes the TTS1.
On my W11 PC it landed on C:/program/Cakewalk/SharedDXi/TTS-1/TTS1-dll

Then I had to select TTS1 in BIAB from the MIDI audio driver setup in the Syntheziser/soundcard option menue (TTS1 appers in the list of options)

I can't remember if I let TTS1 stay in the Cakewalk folder or if I also copied into some BIAB folder.