An internet connection is necessary in order to register a license on a device. Once you are registered, you can use the software offline and you won’t have to login again the next time you launch it, if you don't exceed a certain limit.
Indeed, the software can be accessed offline for 90 consecutive days. If this period is exceeded, you'll need to re-register a license.
Note: you don't need an internet connection to try HeavyM Demo.