WPF UI Not Rendering in Custom Credential Provider Within UAC

Question

I am developing a custom Credential Provider where I launch a WPF application as a Class Library. The WPF window is supposed to display UI elements like buttons and textboxes. However, when the Credential Provider loads and the WPF window appears inside UAC, only an empty window is rendered—no UI controls are visible.

1. When using WinForms instead of WPF, everything works fine inside UAC.
2. The issue only occurs inside UAC mode—outside UAC, WPF renders correctly.
3. I cannot modify the Credential Provider's C++ implementation; the fix must be applied on the WPF side. Why is my WPF UI not rendering correctly within the UAC environment for non Admin user, and how can I fix it while keeping WPF?