Can you perhaps take a screenshot of the navigation bar being in the way of your game?
I also believe that letterbox integer scale isn't actually "full screen" but instead just screen filling.
There's some information about full screen in a browser in the manual here:
https://www.scirra.com/manual/110/browser
Perhaps "request full screen" is something that you want to use if you are playing in a browser.
Hope this helped you in the right direction.