Background: I have a C# automation client (.NET Framework 4.8) using System.Windows.Automation to invoke a button in a Microsoft Access (VBA) application. The target control is non-standard / windowless (AutomationElement.Current.NativeWindowHandle == 0).

Problem: InvokePattern.Invoke() runs without exception and UIA diagnostics look identical when the target window is on the same monitor and when it is on a secondary monitor. However, when the Access window is on a secondary monitor, the button does not actually perform its action even though Invoke() returned normally. When the window is on the same monitor, the action runs as expected.

Environment

• .NET Framework 4.8
• References: UIAutomationClient, UIAutomationTypes
• Target app: Microsoft Access (VBA), windowless controls
• OS: Windows 10/11 (multi-monitor, possibly per-monitor DPI)

Minimal code used

public void ClickButton(AutomationElement button)
{
    object patternObj;

    if (button.TryGetCurrentPattern(InvokePattern.Pattern, out patternObj))
    {
        InvokePattern invokePattern = patternObj as InvokePattern;

        if (invokePattern != null)
        {
            invokePattern.Invoke();
            Application.DoEvents();
            Thread.Sleep(200);
        }
    }
}

Diagnostics logs when it works (same monitor):

=== Diagnostics start ===
IsOffscreen: False
IsEnabled: True
HasKeyboardFocus: False
BoundingRectangle: 0;23;109;24
NativeWindowHandle: 0x0
Supported patterns: InvokePatternIdentifiers.Pattern
TryGetClickablePoint: True -> 54,5;35
Top-level window hwnd: 0x2046A
Foreground window hwnd: 0x2046A
InvokePattern invoked — check whether the button was activated.
=== Diagnostics end ===

When it does NOT work (secondary monitor):

=== Diagnostics start ===
IsOffscreen: False
IsEnabled: True
HasKeyboardFocus: False
BoundingRectangle: 0;23;109;24
NativeWindowHandle: 0x0
Supported patterns: InvokePatternIdentifiers.Pattern
TryGetClickablePoint: True -> 54,5;35
Top-level window hwnd: 0x2046A
Foreground window hwnd: 0x2046A
InvokePattern invoked — check whether the button was activated.
=== Diagnostics end ===

What I already tried

• Verified IsOffscreen, BoundingRectangle, TryGetClickablePoint — they are all identical in both cases
• SetForegroundWindow(topHwnd) and button.SetFocus()
• AutomationElement.FromPoint(clickablePoint) and Invoke on that element.
• AttachThreadInput + SetForegroundWindow before Invoke
• LegacyIAccessiblePattern.DoDefaultAction via reflection (type not available in my runtime)
• As a fallback I used SendInput to simulate a real mouse click — that reliably triggers the button

Observations

• InvokePattern.Invoke executes without throwing in both scenarios
• Element.Current.NativeWindowHandle == 0 (windowless control) — SendMessage(BM_CLICK) to the control is not possible
• The control is exposed to UIA but apparently the provider/target does not perform the action when the window is on the secondary monitor

Questions

1. Has anyone encountered InvokePattern.Invoke returning normally but having no effect when the target is on a different monitor (multi-monitor) ?

2. Are there known UIA / MS Access provider issues with windowless controls or multi-monitor setups?

3. What additional diagnostics would you recommend (ETW, UIA Verifier, MSAA checks, specific properties to compare)?

4. Are there any "clean" alternatives (without moving the mouse) to trigger Access/VBA windowless control actions reliably?