Hello Ernest,
After following the suggested instructions, including deleting and reinstalling the plugin we have finally managed to trace the issue to the wp-content/cache/asp directory, which is strange as we dont have any caching activated within the plugin.
We don’t have a proper fix yet, but have found a workaround in renaming the asp cache directory. At least the filter is working again, but does trigger php warning messages; eg: file_put_contents(/wp-content/cache/asp/search1.css): Failed to open stream: No such file or directory.
Can you investigate if this is indeed a bug or how we may properly resolve this error.
Thank you for your support,
Marcel