Please make sure that you have installed a mobile scan app. Refer to this guide to check mobile scanner app: https://www.bc-scanner.netkiller.com/mobile-scan-app-install
And then you may clear cookie/caches on your browser and retry with below link. In the main page of app, click 'scan' button within the mobile web browser.
(short url: https://goo.gl/ezPoGm)