A monitor that fails to return after sleep needs a consistent wake sequence before it needs a collection of unrelated setting changes. The computer, dock and display may each enter a different low-power state. Record which part wakes and which remains unavailable so that a missing screen can be separated from a computer that has not actually resumed.
Define a repeatable sleep and wake sequence
Save open work, leave both monitors showing ordinary desktop content and let the computer enter sleep through its normal control. Note whether the monitors sleep later on their own timers. Wake the computer using the same input method each time, then allow enough time for the dock and screens to reconnect before deciding the second display has failed.
Check the missing monitor's power indicator and on-screen menu. If its menu opens, confirm the selected input and whether it reports no signal. Inspect the operating system's display settings on the working screen to see whether the missing monitor is still detected. A detected but black display provides different evidence from one that has vanished completely from the arrangement.
Compare waking with both screens connected against connecting the missing screen after the computer has resumed. Change only that sequence. If the latter reliably works, record it as a temporary recovery method and a diagnostic clue. Avoid assuming that any successful unplug-and-reconnect proves the monitor, cable or dock is individually at fault.
Compare the power states along the route
Review the relevant manufacturer's guidance for sleep, deep-sleep, input detection and dock power settings. Names and effects vary between products. Record the existing configuration before changing one supported option, and check both ordinary sleep and a longer idle period. A setting that improves wake behavior may also alter standby power or automatic input switching.
If possible, compare a supported direct video connection with the dock route. Use the same monitor and a documented mode, noting any changed cable or adapter. A successful direct wake narrows the investigation toward differences in the route; it does not identify the failing component without further comparisons. Include dock power and any shared USB devices in the record.
Check driver, operating-system and dock firmware information from the relevant vendors. Apply an update deliberately with a recoverable starting point and the required power arrangement. Updating several components and changing power settings together makes it difficult to learn which step mattered, and it can leave a new regression without a clear route back.
Repeat the original sleep and wake test after a change, including the normal lid position and connected peripherals. Keep the verified recovery sequence available until stability is established over ordinary use. When requesting support, provide the passing and failing sequences, device identifiers and current versions so the report describes a reproducible wake problem rather than a vague intermittent blank screen.