Found the problem, had to use:
$('.adsbygoogle').is(':hidden'))
for ABP. So in the if statement:
function detectAdBlock() {
if($('.adsbygoogle').css('display') == 'none' || $('.adsbygoogle').is(':hidden')) {
$('.adblock').css('display', 'block');
$('.adfail').css('display', 'block');
} else {
$('.adblock').css('display', 'none');
$('.adfail').css('display', 'none');
}
}
$(detectAdBlock);