"no mountable file system" on Mac when trying to install via DMG

A small but noticeable number of Mac users are unable to open our DMG installer for Mac. The Mac presents a "no mountable file system" error when the user attempts to open the DMG for installation.

Each time we try to follow up (these reports come via e-mail), we don't hear back but would like to get to the bottom of this. We aren't able to reproduce the problem on our end.

1) If you are encountering this issue, please follow step (3) on this page, let us know what you see in Terminal, so we can have a closer look at this.

2) Let us know what version of OS X you're on.

Thanks!

MacOS Mojave 10.14.5
$ hdiutil attach -verbose /Users/bryon/Downloads/Stencyl-full.dmg
Initializing…
DIBackingStoreInstantiatorProbe: interface  0, score      100, CBSDBackingStore
DIBackingStoreInstantiatorProbe: interface  1, score    -1000, CBundleBackingStore
DIBackingStoreInstantiatorProbe: interface  2, score    -1000, CRAMBackingStore
DIBackingStoreInstantiatorProbe: interface  3, score      100, CCarbonBackingStore
DIBackingStoreInstantiatorProbe: interface  4, score    -1000, CDevBackingStore
DIBackingStoreInstantiatorProbe: interface  5, score    -1000, CCURLBackingStore
DIBackingStoreInstantiatorProbe: interface  6, score    -1000, CVectoredBackingStore
Attaching…
2019-06-25 13:24:16.028 diskimages-helper[30064:4016845] -remountReturningDictionary: detaching because no mountable filesystems.
Error 112 (no mountable file systems).
Finishing…
DIHLDiskImageAttach() returned 112
hdiutil: attach failed - no mountable file systems

First, check that the file was downloaded correctly. The MD5 should be 0ca8a6839ff1c5651b1aac1fd9ffc80e. Here are instructions.

If it's different, try redownloading the file. If the md5 is the same, also try following steps 2, 5, and 6, if applicable, from the guide linked to in the first post.

If all of that seems to be fine, see if you can open the dmg in safe mode. If opening the dmg in safe mode did the trick, you can keep following the posts in the linked guide to see how to inspect your system modifications to try to figure out what's causing your computer to fail to mount the dmg normally.

It is not working

Is this the issue that can be solved by dragging the app onto the desktop then back into the folder? Could be a different issue but I remember having to do that.