High Sierra and DMG files "no mountable file systems"

[roiegat]

Anyone else having issues opening any DMG files in High Sierra? I was trying to upgrade both flash and java on the test machine. Both come down as DMGs and when I tried to open it I got an error saying there is "no mountable files systems". Doing a quick google search didn't find anything helpful.

The only thing I can think of is that the machine is on APFS....but can't seem to find a fix right now. I've resorted to opening it on another machine and moving the files over afterwards.

[aspears]

Yes, I've been experiencing that same issue but not just on High Sierra machines. The DMG works on some machines and not others.
I still haven't found a cause or fix yet

[jedi1yoda1]

I had a client recently with this issue. They deployed a DMG package to 4500 computers and around 10% of them had this issue. I noticed in some of cases, it was due to the download been interrupted (they do have bandwidth issues), but most of them had completed the download OK. I found that the package was built with an older version of Composer on an older version of the OS. I rebuilt the package using the latest version of Composer on the latest macOS (at the time 9.101 and 10.13.1 respectively) and we redeployed the package to the same set of computers (all on 10.13+). I saw a less than .1% error rate with the package built with the latest versions. Their JSS was not up-to-date at the time, but using the newer version of composer should not matter.

Note: All volumes involved in this scenario were HFS+, nothing yet on APFS (their environment is entirely mechanical HDDs).

[mbracco]

We had the same. Analyzine the dmg we found a APFS Container inside, which was not readable by computers in 10.12.x.
May be your issue ?