Nothing happens when I press a capture hotkey.
macOS requires Screen Recording permission before any app can read the screen, and it asks the first time you take a capture rather than at launch. Open System Settings, choose Privacy and Security, then Screen Recording, and turn Lasso on. If macOS offers to quit and reopen the app, take it: the permission only reaches an app that starts fresh afterwards. Then try the hotkey again.
What are the hotkeys?
Control Shift 1 draws a freehand selection, Control Shift 2 drags a rectangle, Control Shift 3 takes the whole display, and Control Shift 4 picks a window. Every one of them is also a button in the menu bar menu, and you can rebind them there.
My freehand capture came out as a rectangle.
Lasso clips a freehand capture to the shape you drew, leaving everything outside it transparent. If you are getting the rectangle around your shape instead, open the menu bar menu and check that Clip Freehand to Path is switched on. Turn it off any time you would rather have the plain rectangle.
How do I cancel a capture?
Press Escape. Clicking without dragging cancels too, as does pressing any capture hotkey while the overlay is already up. The frozen, dimmed screen you see during a capture is an overlay; cancelling puts everything back exactly as it was.
What happens after I capture?
The image goes straight to your clipboard, so you can paste it immediately, and a thumbnail appears in the corner with Copy, Save, and share buttons. It fades on its own after a few seconds; move the pointer over it to keep it around. Save opens the standard save panel and remembers the folder you used last.
I have two displays. Which one does it capture?
The one your pointer is on. Move the pointer to the display you want and then press the hotkey.
There is no icon in the Dock.
That is deliberate. Lasso lives in the menu bar and stays out of the Dock and the app switcher. Click the camera icon in the menu bar for the menu, which is also where you quit.
Where do my screenshots go?
Onto your clipboard, and into the file you choose when you save. Lasso keeps no library and no history, has no account and no server, and sends nothing anywhere. See the privacy policy for the full picture.
Contact
Email cody@adventinnovation.com with your Mac model, the macOS version, and what you were doing when the problem happened. Screenshots help, and you have a good tool for those.