Why won't Premiere Pro launch when I "Start Editing" my Project?

If Premiere Pro doesn't launch, you likely have an unsupported version installed on your workstation. Remove the older versions of Premiere Pro, then PostLab will launch.

Have multiple versions of Premiere Pro installed? PostLab will also detect those, then prompt you to launch the desired version.

Change Default Project Version takes you to Preferences > Templates. Then you can set which Premiere Pro Project version will be used as the DEFAULT EMPTY PROJECT when adding Projects as Documents to a Production.