Unified installer not upgrading to pro for some licensed users

We recently deployed the 64-bit unified installer. For the most part it works great, standard users get basic Reader functionality, and licensed users can sign-in and get the install upgraded to Pro.

However, there are several of our Pro licensed users that never get prompted to upgrade to Pro after signing in. We have uninstalled/reinstalled dozens of times, signed-in and out, ran the Adobe cleaner tool, etc.

Why do some users just never get the prompt to upgrade to Pro? Is this a client issue or license issue? Is there a way to trigger the "upgrade" process when a licensed user is signed-in? It seems to be an automated process that happens upon sign-in, but no way to manually trigger it.