Tested with puppet 4.7.0
$ puppet module install --modulepath=/tmp/foo simp-simplib
Notice: Preparing to install into /tmp/foo ...
Notice: Created target directory /tmp/foo
Notice: Downloading from https://forgeapi.puppetlabs.com ...
Error: Could not install module 'simp-simplib' (???)
No version of 'simp-simplib' can satisfy all dependencies
Use `puppet module install --ignore-dependencies` to install only this module
After much spelunking it turns out that one of the version-constrained dependencies was not yet released onto the forge.
$ puppet module install simp-simplib
Installing would require herculesteam/augeasproviders_sysctl (>= 2.1.0 < 3.0.0) but it is not available.
Trevor Vaughan in what context are you using puppet module install rather than r10k/code manager?
The original way :-D.
Also, when r10k and CM don't do what you expect, this is how you see if it's a problem with the Forge call, or something else.
Better fixed by improvements to r10k/code manager dependency resolution
PUP-9176 has steps to reproduce, so I'm closing this as a dup.