Could you enable error logging in the Troubleshooting section of Advanced tab at PageSpeed Ninja settings page, reload page with issue, disable error logging, and check for possible warning messages in wp-content/plugins/psn-pagespeed-ninja/includes/error_log.php?
And which HTML Parser option do you use?
PHP version: 5.6.35
Interface: CGI/1.1
Server API: cgi-fcgi
Server: Apache
OS: Linux biz150.inmotionhosting.com SMP Sun Feb 18 08:20:42 EST 2018 x86_64
Wordpress version: 4.9.6
Activated plugins:
Gravity Forms 2.2.6 (gravityforms/gravityforms.php)
Duplicate Page And Post 2.1.1 (duplicate-page-and-post/duplicate-page-and-post.php)
Fusion Builder 1.5.2 (fusion-builder/fusion-builder.php)
Fusion Core 3.5.2 (fusion-core/fusion-core.php)
Gravity Forms PayPal Standard Add-On 2.9 (gravityformspaypal/paypal.php)
GravityWP – CSS Selector 0.2.2 (gravitywp-css-selector/gravitywp-css-selector.php)
Loginizer 1.4.0 (loginizer/loginizer.php)
PageSpeed Ninja 0.9.26 (psn-pagespeed-ninja/pagespeedninja.php)
Shortcode Cleaner Lite 1.0.6 (shortcode-cleaner-lite/shortcode-cleaner-lite.php)
UpdraftPlus – Backup/Restore 1.14.11 (updraftplus/updraftplus.php)
Yoast SEO 7.6.1 (wordpress-seo/wp-seo.php)
WP-Optimize 2.2.4 (wp-optimize/wp-optimize.php)
Smush 2.7.9.1 (wp-smushit/wp-smush.php)
WP Super Cache 1.6.1 (wp-super-cache/wp-cache.php)
*/
?>
[Mon, 18 Jun 2018 21:28:33 +0000] WARNING: filemtime(): stat failed for /home/———————/wp-content/plugins/psn-pagespeed-ninja/cache/pagecache.stamp in /home/———————/wp-content/plugins/psn-pagespeed-ninja/admin/class-pagespeedninja-admin.php on line 120
/home/———————/wp-content/plugins/psn-pagespeed-ninja/admin/class-pagespeedninja-admin.php:120 <- /home/———————/wp-includes/class-wp-hook.php:286 <- /home/———————/wp-includes/class-wp-hook.php:310 <- /home/———————/wp-includes/plugin.php:453 <- /home/———————/wp-admin/admin-header.php:118 <- /home/———————/wp-admin/admin.php:216 <- /home/———————/wp-admin/options-general.php:10
