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 →Monitor Refresh Rate TestEstimate display refresh timing using animation frames.
Run →Decision table
What the observation changes
ObservationWhat it meansNext action
HDMI works, USB-C dock does notDisplay itself works; USB-C/dock path is higher priority.Test direct USB-C/DisplayPort and dock upstream cable.
Neither HDMI nor USB-C works with same monitorMonitor input/config or graphics state becomes more likely.Test a second known-good monitor/cable and Lenovo/Windows display diagnostics.
Only high refresh/resolution failsBandwidth/cable/dock limit is plausible.Lower mode, then verify dock/cable specification.
Sequence
Work from reversible checks to escalation
- 01
Select correct monitor input.
- 02
Test native HDMI direct.
- 03
Test Thunderbolt/USB-C direct if display supports it.
- 04
Add dock only after direct paths are understood.
Likely areas
Keep these branches separate
Dock/cable pathWrong display inputThunderbolt/USB-C negotiationGraphics/OS state
Repair boundary
When to stop changing settings
If native outputs fail across known-good displays/cables, use Lenovo Vantage/diagnostics and support.