Starting with v2.0.31, GeForce NOW has stopped supporting macOS 10.10 with native app.
If you want to use the native macOS app, you can download this v2.0.30 app which will not receive software updates. This app will continue to work for a few months until we update our GeForce NOW server software with new security enhancements. At that time, this app will no longer work and you will need to upgrade to macOS 10.11 or later.
You can continue to play using Google Chrome browser by visiting https://play.geforcenow.com