We have chosen to not set up a Shortcut by default to launch Runner Pro. Conflicting shortcuts in Sketch are a pain to manage, and shortcuts generally only work well for specific keyboard layouts. Set up a hotkey that works well for your situation on first use.
Go to Plugins › Runner Pro › Settings in the menu bar and select the Shortcuts tab. Here you can set your favorite Shortcut for all Runner commands, for
Run Last Action, Toggling the visibility of RunBar, and navigating forward and backward between Artboards.
Check out the Sketch Documentation to see if your intended Shortcut isn't clashing with one that's already defined.
If you frequently Run the same action one after another, you can set a shortcut to execute it rightaway and bypass launching the Runner search window.