Start with evidence
Run the tests that separate the likely branches
USB-C Display Path Readiness CheckCheck four documented prerequisites for sending video through USB-C, Thunderbolt, a dock, cable or adapter to a display.
Run →Screen Resolution TestShow browser viewport, screen dimensions, and device pixel ratio.
Run →Display Raw Bandwidth CalculatorEstimate raw uncompressed pixel data rate from resolution and refresh rate.
Run →Decision table
What the observation changes
ObservationWhat it meansNext action
HDMI works but USB-C video does notGPU/display itself can drive an external monitor; focus on USB-C video path.Test a known video-capable Type-C cable direct to each documented video-capable port.
Direct USB-C works but dock does notDock/upstream cable/topology is implicated.Check dock display spec and upstream cable.
No external output worksThis is broader than one USB-C port.Check GPU/display mode and run Dell diagnostics.
Sequence
Work from reversible checks to escalation
- 01
Select the correct monitor input.
- 02
Remove the dock and test direct.
- 03
Use a known DisplayPort-capable USB-C cable/adapter.
- 04
Temporarily lower resolution/refresh and retest.
Likely areas
Keep these branches separate
Cable lacks DisplayPort Alt ModeDock/adapterWrong monitor inputResolution/refresh combinationLaptop port/driver
Repair boundary
When to stop changing settings
If HDMI and both documented USB-C display paths fail with known-good displays/cables, run Dell diagnostics and contact support.