I've got a 2.6MB .dmg file and under More Info there appears simply "--".
Moreover, when I try to open/mount it, I get a window with the message "No mountable file systems" — something which I've never seen before. Contacting the company's IT support, I'm advised to set my Security & Privacy setting to allow downloads from Anywhere, which has always been the case — so that wouldn't seem to be the problem. IT support has not followed up.
Sounds like the IT department is either not listening to what you are saying or they are blowing you off. No mountable file system has absolutely nothing to do with your security settings but I suspect it is a problem their IT department runs into pretty commonly. The real problem is almost always one of two things.
- A download error in which case downloading the file a second time is almost always a sovereign cure or…
- An error in building the .dmg in which case the only cure is the originator has to rebuild the .dmg and you have to download it again.
It is an error I have encountered many times over the years — even in downloads from Apple. Thinking back on it, I don't recall seeing that error for at least a couple of years or more. Maybe since Mountain Lion but I would not swear to that and I am not propounding a cause and effect either.
By-the-way I have my download settings set to
Mac App Store and identified developers and in Mavericks and Yosemite if a downloaded application won't install because it is not from the App Store or an identified developer after acknowledging the refusal, if you open System Preferences → security & Privacy a note will appear in the System Preferences window that application X was not installed do you wish to continue with the install anyway, click on Continue and the installer reappears and the installation proceeds without further interruption. I leave it that way just in case I get careless as it makes me stop and think about what I am doing.
