Installation finished. Truss Tape Plus is in Applications and should open now.

There is no separate app window. The shop is a browser tab at http://local.trusstapeplus.com:8877/ (this Mac, not the public website). Give it about 15 seconds the first time while the app unpacks.

The Dock icon is Truss Tape Plus running. Click it to open or bring back the shop tab. Quit from the Dock (or Command-Q) when you are done. Closing the browser tab does not quit the app.

If nothing appears, open Finder → Applications → Truss Tape Plus. Do not use Launchpad if this Mac has other copies of the same app.