Correct way to install on multisite

Hi,
I find this plugin essential on a large multisite (1000s of sites) I manage.
However, I’ve not found a way of using it site wide.

1. Network Activate does not work due to ‘fatal error’. I’ve increased the memory WP_MEMORY_LIMIT in wp-config.php to no effect

2. I’ve tried adding it to the mu=plugins dir calling it from a file:
require WPMU_PLUGIN_DIR.’/wordpress-https/wordpress-https.php’;
This works for other plugins, but when I do this for this plugin all sites stop working properly – clicking menu items only loads the homepage and other anomolies.

Is there a correct way of installing this in multisite? I just want the snippet that converts all images / links / embedded media / youtube links from http to https to prevent the mixed content warning.

Any help you can give with this would be fantastic.
Thank you,

Alex Furr

https://www.ads-software.com/plugins/wordpress-https/