CivilPro cloud requires an internet connection.
CivilPro desktop does not require internet ONLY IF you are creating stand-alone projects (saving to your desktop).
If you are connecting your Desktop to a SQL server (for your data), CivilPro desktop requires an internet connection.
If you have the Plus plan (Desktop + Cloud), CivilPro desktop requires and internet connection.
The only way to work offline is if you have CivilPro desktop and you are creating stand-alone projects that are saved to your desktop.
There is no way to sync an offline project to the cloud (eg. if you have the Plus plan, or want to change it/connect it to a SQL server).
The only time we recommend that you work offline by creating stand-alone projects if more than 70% of the project needs to be worked on from a remote site without access to an internet connection.