If you are logged in in Steam (desktop) and can't open the browser, try this:

Open this link: in your browser
Go to your Steam client, tab Console
Enter:
app_license_request 1227750 (main game)
app_license_request 1404900 (levels pack 1)
app_license_request 1404901 (levels pack 2)
app_license_request 1404910 (levels pack 3)

It should do the same as the instructions in Medeiros's link.
To verify, go to the Store pages and you should see text like this:


How do I know the numbers from above? They're in the store links:
https://store.steampowered.com/app/1227750/Puzzle__LINES_AND_KNOTS/

Tags: addfreelicense !asf register free license steam