Show/Open new XF page from custom rendered

For some reason I had to implement custom renderer for one of the pages in my app

Now I need to navigate to another (modal) XF page upon some user action on this custom renderer page.
When tried to call Navigation.PushModalAsync (new XF_Page3 ()); from it, .......... it does not display the XF_Page3

e.g. XF_Page1 ----> XF_CR_Page2 --------> XF_Page3

Here XF_CR_page2 is custom rendered (as a new activity in Android)