This app (formerly known as Greek WPA Finder) was originally intended for use inside Greece as it can recover default WPA/WPS Keys of specific router brands that are popular within Greece thus helping you test your network security.
Nowadays there is an ongoing effort to gradually support more routers around the world.
If you are not located inside Greece you can still try your luck with this app but don't be frustrated if it doesn't fully work in your territory.
In case you manage to connect to a network othen than yours, you have to inform the owner so that he/she changes password.
Have a look at the GWPA Finder – FAQs here: https://thanosfisherman.github.io/posts/gwpa-faqs/