Hi,
Thank you very much for the details!
I logged in, activated the plugin, but I get the same exact output (the correct one). This means, that this is only a cache issue. The style may have been changed prior the plugin activation and if there is an aggressive cache, then it may serve the cached files from that state.
Purging the cache (click Purge SG Cache) as well as clearing all other layers of cache (Cloudflare, CDN, browser etc..) will resolve the issue 🙂