plugin not available in multisite

I have the very same issue. I hope someone helps us!

The plugin is only accessible from the Network Admin screen. We don’t provide a way to configure this on individual subsites at the moment, but it will upload all media library assets across the entire network.

Ah, so it is “on” for all sites if we need it for one. Thanks for the answer!

Is it possible to disable CDN on a specific child website and leave it enabled on other child and parent websites?

That will be a future feature of the upcoming Pro upgrade, which you can get news and updates about here https://deliciousbrains.com/email-subscribe/3/