I've certainly run Captivate for days at a time without an internet connection, for example, when I'm travelling. Still, there are a couple of times when you need the internet, even if it's temporary. First and foremost is when you activate the software. I would recommend a perpetual license so that your software isn't constantly checking for the status of your monthly subscription (even though it requires a year-long commitment at first). There are a handful of other features that need an internet connection to function, namely the resources from the assets store. Another such feature would be the use of Adobe fonts. Without an internet connection, you couldn't download and use fonts from Adobe Fonts. I believe Adobe fonts require an internet connection during the publishing process as well.
Thank you very much for your reply. My initial concern, though, was for the installation of Captivate on that network where no Internet connection is possible. As for the fonts, I do not require much in that field so the default settings will be fine by me.