2. UD-CA1A HDMI Video Not Working, U...

UD-CA1A HDMI Video Not Working, USB-C Alt Mode Compatibility Checklist

Last Update: December 31st, 2025
Article ID: 3642881

Overview

If your external monitor is not receiving a signal when connected to the HDMI port on the Plugable UD-CA1A docking station, the cause is almost always related to USB-C port compatibility or cabling.

The UD-CA1A uses USB-C DisplayPort Alternate Mode for video output. It does not use DisplayLink and does not require video drivers. If HDMI video is not working, the issue is typically not software-related.

Follow the checklist below to identify and resolve the issue.

Troubleshooting Checklist

1. Confirm Host Computer USB-C Video Support (Alt Mode)

Not all USB-C ports support video output.

Requirement

  • The USB-C port must support DisplayPort Alternate Mode, Thunderbolt 3 or 4

Not Supported

  • Host USB-C ports labelled as data only
  • Host USB-C ports intended for charging only

How to Check

  • Review the laptop or system manufacturer’s specifications
  • Look for a DisplayPort icon or lightning bolt symbol near the USB-C port

If the USB-C port does not support DP Alt Mode or Thunderbolt, HDMI video will not function through the dock.

2. Use the Correct USB-C Cable

The USB-C cable is critical for video functionality.

Action

  • Use the USB-C to USB-C cable included with the UD-CA1A.

Important

  • The cable must support Alt-Mode Video 
  • Many third-party or phone charging cables are USB 2.0 only and cannot carry video.
  • USB-C connectors may fit physically, but still lack the internal wiring required for video

Always test using the original included cable first.

3. Check Monitor Input and Display Limits

Most Common Causes for No Video

  • The laptop’s USB-C port does not support video output
  • A charging-only or USB 2.0 USB-C cable is being used

Monitor Input

  • Manually set the monitor’s input source to the correct HDMI port, such as HDMI 1 or HDMI 2
  • Some monitors do not automatically switch inputs

Single Display Limitation

  • The UD-CA1A supports one external display only
  • Multiple monitors are not supported.

HDMI Cable

  • Use a direct HDMI cable from the dock to the monitor
  • Avoid adapters, converters, or HDMI splitters

4. Power Cycle the Dock

Resetting the dock can resolve HDMI handshake issues.

  1. Disconnect the USB-C cable from your laptop.
  2. Disconnect the power adapter from the back of the dock.
  3. Wait 30 seconds for the dock to discharge fully.
  4. Reconnect the power adapter to the dock.
  5. Reconnect the USB-C cable to your laptop.

Still No Video?

If you have confirmed all steps above and the HDMI video is still not working, additional diagnostics may be required.

  1. Please download and run our diagnostics tool: PlugDebug.
  2. Email the resulting ZIP file to support@plugable.com and mention the steps you've already tried.