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
Monitor works when connected directly but not through dockLaptop-to-display output is partly proven; dock/cable/topology is the dividing line.Use the dock's intended Thunderbolt/full-featured upstream cable and check dock display support.
Dock charges laptop but USB/video both failPower delivery is working but data/display lanes are not proven.Replace/reseat the upstream cable and test another host port.
Known-good display fails directly on both laptop portsThe problem is broader than the dock.Run Dell SupportAssist/pre-boot diagnostics and check firmware/support.
Sequence
Work from reversible checks to escalation
- 01
Test one display directly to the XPS first.
- 02
Use the dock's certified upstream cable.
- 03
Select the monitor's exact input and reduce to one display.
- 04
Add dock/peripherals back one at a time.
Likely areas
Keep these branches separate
Dock upstream cableDock display topologyMonitor input/cableThunderbolt/USB4 negotiationLaptop port or firmware
Repair boundary
When to stop changing settings
If both Thunderbolt ports fail with known-good direct DisplayPort/Thunderbolt paths, run Dell diagnostics and contact Dell support.