The window opens on the discrete GPU now, which fixes "nothing happens when I run it".
A reporter's Windows event record finally named the cause (#32):
AppName dlss5oneclick.exe AppVersion 0.11.14.0
moduleName atio6axx.dll ExceptionCode c00000005
ModulePath ...\amdogl.inf_amd64_...\atio6axx.dll
atio6axx.dll is AMD's OpenGL driver. This app draws with OpenGL, and on a hybrid machine the window can land on the integrated part; there, the driver faulted before any of my code ran — which is exactly why nothing appeared: no window, no message box, and no %LOCALAPPDATA%\dlss5oneclick\gui-error.txt, because the crash handler had not been installed yet.
The exe now exports NvOptimusEnablement and AmdPowerXpressRequestHighPerformance, the two symbols NVIDIA's and AMD's drivers read from the export table to put a process on the high-performance GPU. Verified with dumpbin /exports on the shipped binary.
If the app still does nothing on your machine, that event record is the thing to post — Event Viewer ▸ Windows Logs ▸ Application, the entry naming dlss5oneclick.exe.