Hi Michelle,
I am an Independent Advisor and I'm happy to help you.
Since you've already tried running the Surface Diagnostic Toolkit, updating Windows, and reinstalling the touchpad driver, let's proceed with checking the Touchpad settings.
- Open Settings (Press [Windows] + [I]).
- Go to Devices > Touchpad.
- Scroll down to the Taps section and ensure that Tap with two fingers to right-click is enabled.
- Scroll down to the Drag and drop or Three-finger gestures section and make sure dragging is enabled.
- If needed, reset the touchpad settings to default by clicking Reset under "Reset your touchpad."
After making these changes, test if right-click and click-and-drag work properly.
Let me know if this helps!