Infinite Scroll not working in own theme

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You need either a content.php or content-<post format>.php OR use a render:

add_theme_support( 'infinite-scroll', array(
    'container'  => 'content',
    'footer' => false,
    'render' => 'render_function',
    'wrapper' => false
) );

function render_function() {
    get_template_part('loop');
}

This implies you have a loop.php.