pen eraser button not working

I'm having an issue where my stylus's eraser button (side button) no longer works as an eraser shortcut in Photoshop, even though it used to work fine before.

My setup:

• Laptop: Lenovo Yoga Duet 2020 (2-in-1 tablet with built-in active pen, non-Wacom)
• Photoshop version: 2024 (please let me know if I should share the exact build number from Help > System Info)
• OS: Windows 10

Symptom:

• Pressing the pen's side button no longer triggers the eraser tool in Photoshop.
• I confirmed this is NOT a hardware/driver issue — the pen's button works perfectly for erasing in OneNote and other native Windows Ink apps.
• This means Windows Ink itself is working correctly; the problem seems isolated to how Photoshop interprets the pen's eraser signal.

What I've tried:

• Reset the Eraser tool (right-click in options bar > Reset Tool)
• Confirmed "Spring-loaded Keyboard Shortcuts" is enabled in Preferences > General
• Checked layer isn't locked (transparent pixels lock is off)
• Briefly tried forcing WinTab mode via PSUserConfig.txt (UseSystemStylus 0) — this actually broke pen input entirely, since my pen has no WinTab driver support, only Windows Ink. Reverted this change.