No, you can use Microsoft 365 Apps for Enterprise offline. However, you must be connected to the internet during the installation so that the activation can be completed. After that, you are only required to connect to the internet once every 30 days to keep your software fully functional. If your computer is offline for more than 30 days, Microsoft Office will enter a Read-Only mode until the next time you connect to the internet.
Last modified: March 16, 2021