GUI stopped working?

[AlleyArtwork]

Hi All,
I'm hoping someone might know a place to start troubleshooting a strange issue.

I have a compiled app, gui and all that's worked for roughly the last 3 years.
There have been no changes to the code, but there has been a change on the environment.

After running the app on a newly deployed laptop, The app stopped drawing the GUI window (but IS still "running"; it can be seen in Taskbar & System Tray, and the built in functions/hotkeys native to the app actually work).

At first, i thought it was because of Windows 1809: all of the users reporting this issue were on this version, and all of the users it was still working for were on older version, but then i reached out to a wider audience and asked for a report for working/not working, and there are W10 1809 users not experiencing the issue and the GUI window is loaded like they've always seen.

Application is running from a location on the laptop that user has Full Control permissions on (in A_MyDocuments).
I don't expect a solution, i'm mostly hoping someone might know a decent place to begin looking. I feel like this is user permission related somehow but i don't have enough data to accuse any one thing yet.