Hi Jacob and thanks for your quick reply.
I’m currently using 2012 but I’ve also tried 2011. Here’s a test page: https://edlunddesign.com/hej-varlden/ PB works fine for the image in the body but not for the featured image.
I have added the path https://mydomain.com/wp-content/plugins/pb-responsive-images/slir/ for SLIR but I guess that mod_rewrite is working like it should..? At least in the .htaccess I see:
RewriteRule ^wp-content/plugins/pb-responsive-images/slir/(.*)$ /wp-content/plugins/pb-responsive-images/slir/index.php?r=$1 [QSA,L]