Treadle carries out actions on your Mac, so macOS asks you to grant three permissions. The first-run wizard requests them. You grant each one in System Settings under Privacy & Security. See also Install Treadle.
Accessibility
Treadle uses Accessibility to press keys and move windows for you. This covers opening Spotlight, locking the screen, arranging windows, and typing a snippet.
Without it, those buttons do nothing and show no error.
After you grant Accessibility, the engine restarts so the change takes effect. That is normal. (See concepts for what the engine is.)
Screen Recording
Treadle needs Screen Recording to take screenshots. macOS counts capturing the screen as recording it, even for a single still image.
Without it, screenshots come out black or empty.
Automation
Treadle needs Automation to tell other apps what to do, such as play or pause Music, quit an app, or empty the Trash.
macOS asks the first time Treadle controls each app. If you decline, that app's actions will not work until you allow it.
If a button still does nothing
A silent, do-nothing button is almost always a missing permission. Open the menu-bar popover and check Diagnostics, which names the missing permission and the fix. See A button does nothing when I press it.