Theme bug when using custom index.php

[glukose]

Hi,

I ran into a trouble when installaling a pro theme (avada), menus, images and effects were not displayed properly or at all.

I started a clean install, charging the theme first and without changing index.php, I had the expected result.
But using the custom index.php, I loose the menu instantly.

I really don't know what to look for, what could cause such result.

Thanks,

Clément