Hello i am trying One page parallax and i found few issue
main one is :
On mobile the main parallax header isnt working
even your demo ( http://themes.semicolonweb.com/html/canvas/op-parallax.html ) if loaded directly on mobile is not working
second issue which i been able to resolve but i suggestion you to fix on next release:
the one page demo have a section araund middle page with paralx ( the one with rewives) if you remove this section even on desktop the parallax is not workign anymore .... so i had to add parallax class to main parallax on top of the page on div id slider,
