You do not need to be online to continue working on a cloud project. There are two situations that can occur:
Your Internet connection was interrupted while you were working on a Citavi project.
You can continue working and close your project when you're done. As soon as the Internet connection is available again, Citavi will synchronized your changes with the Citavi Cloud.
Your Internet connection was interrupted before you could open a Citavi project.
The cloud project does not appear in the list of recently opened projects. On the Welcome Screen, click Open project. You'll find your project on the Cloud tab. Click the project name to open it.
If you're working offline, you can't attach PDF files to a reference, add image or file quotations or add cover images.