There was an older firmware version where the unit may have main volume set to silent when powering up (
ref. here). This has been fixed in later firmware version, so make sure your's is up to date.
The latest version is 1.41, but for some very strange reason it's not posted on the Origin
resource page. You really want 1.40/1.41 as it contains new features and modules as well as bug-fixes. You may want to ask Arturia if they have the files available. There is also a manual, version 1.3 which isn't on the resource page.