After upgrading to 3.0.4 I got issues with other plugins.
I get this kind of code in other plugins:
if ($_SERVER['HTTPS'] == 'on') $planyo_files_location = str_replace("http:","https:",$planyo_files_location);
Now even if I comment the if line, somehow the HTTPS plugin prevents (or reverts?) this setting and all scripts cannot be loaded anymore because of this kind of errors:
XMLHttpRequest cannot load http://www.dentfix.ro/wp-content/plugins/planyo-online-reservation-system/ulap.php. Origin https://www.dentfix.ro is not allowed by Access-Control-Allow-Origin.