USB-C Display Output Not Working on HP EliteBook 840 G8

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Issue: USB-C Display Output Not Working on HP EliteBook 840 G8
Device details:

• Model: HP EliteBook 840 G8 Notebook PC
• Product Number: 515V5UC#ABA
• OS: Windows 10/11 (local account, Windows Hello enabled)

Problem:

• My laptop is not outputting display through USB-C, even though:
• The same USB-C → HDMI adapter and cable work on my HP Victus, confirming they are functional.
• USB-C data/charging works, but no video signal is detected on external monitors.

What I’ve tried so far:

• Enabled BIOS options:
  • USB Type-C Connector System Software Interface
  • Enable High Resolution Mode When Connected to a USB-C DP Alt Mode Dock
• Disabled Kernel DMA Protection (it didn’t affect anything).
• Updated BIOS and drivers.
• Checked Windows and HP support pages for documentation about DP Alt Mode.
• Looked through BIOS for Thunderbolt/USB-C security restrictions.
• Verified multiple monitors and HDMI ports.
• Tried system restart, cold boot, and dock disconnect/reconnect.

Symptoms:

• Monitor shows “No signal”.
• Windows does detect the display and screen can be shared on google meets/teams.  Also I can drag windows to the  screen.
• No hot-plug events appear in Device Manager or Event Viewer.
• USB-C port otherwise works for non-display functions.

Additional context:

• The laptop’s documentation is unclear/inconsistent about whether this specific configuration (515V5UC#ABA) supports DisplayPort Alt Mode over USB-C.
• BIOS changes related to security temporarily disabled Windows Hello login options (PIN + fingerprint), but those were resolved.

What I need help confirming:

• Does the HP EliteBook 840 G8 (product number 515V5UC#ABA) support USB-C DisplayPort Alt Mode for video output?

If yes:

• Which BIOS settings or drivers are required to enable it?
• Are there known issues with this model’s USB-C video output?

If no:

• Is the lack of DP Alt Mode specific to this configuration / region variant?