After upgrading my WiX project from WiX v3.11 to WiX v5, the following problems have arisen:

• The main window of the bootstrapper application displays only the title bar, with the rest of the window remaining white.
• Icons and other UI elements (buttons, text, images) that were previously visible are no longer displayed.

I tried the below things:

1. Simplified Theme File: I have attempted to create a minimal theme.xml file to isolate the problem, but the issue persists.
2. Verbose Logging: Enabled verbose logging to gather more details, but the logs have not provided sufficient information to resolve the issue.
3. Predefined Theme: Tested with predefined themes provided by WiX to determine if the issue was specific to the custom theme, but the problem continues to occur.
4. Correct Paths: Verified that all paths to theme files and resources are correctly specified and accessible.

Please find below the simplified code of Theme.xml file

<?xml version="1.0" encoding="UTF-8"?>
<Theme xmlns="http://wixtoolset.org/schemas/v4/wxs/theme">
    <Font Id="WixUI_Font_Title" Name="Arial" Size="14" Height="20" Bold="yes" />
    <Font Id="WixUI_Font_Normal" Name="Arial" Size="10" Height="13" />
    <Window Id="MainWindow" Width="500" Height="400" Background="white" Title="[ProductName] Setup" FontId="WixUI_Font_Normal" Caption="TestAPP">
        <Text Id="Title" X="10" Y="10" Width="480" Height="30" FontId="WixUI_Font_Title" Caption="Welcome to the [ProductName] setup wizard" />
    <Button Id="NextButton" X="400" Y="350" Width="80" Height="30" Text="Next" />
    <Button Id="CancelButton" X="310" Y="350" Width="80" Height="30" Text="Cancel" />
    </Window>
</Theme>

Despite these efforts, the application window remains mostly white with only the title bar visible.