Run the check
Record the browser estimate while the tab is foregrounded.
Check the operating system's selected display mode and the monitor's own status menu.
Compare cable, port, adapter, and resolution against the device specifications.
Read the result
A 60 Hz system mode needs an OS or connection check before blaming the test.
Limits and next step
Frame callbacks are affected by scheduling and are not a definitive port capability report.
Repeat the check after changing one setting or connection. Keep a record of what changed before deciding whether the device needs service.