Mod_pagespeed installed but filters not running on page. No pagespeed headers present
I've just started a standard LAMP DigitalOcean droplet and installed Google Pagespeed. The package is installed and listed in /etc/apache2/mods-enabled/
I have added the following items to the pagespeed.conf
ModPagespeedEnableFilters prioritize_critical_css ModPagespeedEnableFilters lazyload_images,inline_preview_images,insert_image_dimensions ModPagespeedEnableFilters resize_mobile_images,insert_image_dimensions
Which I have used on previous projects. For some reason none of these filters are being run. Inspecting the headers being passed from the server show no pagespeed headers.
I don't seem to be running across any errors anywhere and I am stuck as to what to look for next.