You must connect to the Internet when you want to install Adobe Creative Cloud apps, such as Photoshop and Illustrator. Once the apps are installed on your computer, you don’t need an ongoing Internet connection to use the apps.
You can use the apps in offline mode with a valid software license for a limited period. The apps attempt to validate your software license every 30 days.

Detailed description:

https://helpx.adobe.com/creative-cloud/kb/internet-connection-creative-cloud-apps.html