Hi Frank, thanks for getting back to me so quickly!
- The plugin is network installed and I've ticked the boxes for Optimise JS and CSS. Do I need to configure anything additional for multi site?
- Exactly the same if I use a default theme
- If I activate HTML optimization, I get white screens
Not sure if this will help but here is a link to the primary site:
and here are links to sites 2 and 3 (which are actually 4 and 5 in terms of folder structure)
They may try and redirect you on the first visit to the English version of the site.
You'll be able to see though, sites 2 and 3 do have some autoptimize css and js files, however they do not contain all of the code (e.g. the style.css is missing) even though the files have been removed from the source code.