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ERROR_INVALID_PRINT_MONITOR
This status differs from ERROR_UNKNOWN_PRINT_MONITOR. An unknown monitor cannot be resolved by name; an invalid monitor reaches validation of a monitor component or registration but the component does not satisfy the print subsystem's required monitor contract.
Port monitors are not arbitrary DLLs. They participate in the spooler architecture that opens ports and transfers raw printer data, and they are installed through monitor-specific management interfaces. A wrong binary, mismatched component set, damaged registration, or unsupported monitor implementation should be investigated at that boundary.
Validate the component, not the printer cable
- Record the exact monitor name, environment, and DLL from the attempted registration or existing MONITOR_INFO_2 entry.
- Compare the installed component with the vendor's intended package and target Windows architecture.
- Check whether the failure follows a partial upgrade or migration that copied queue configuration without the monitor's full installation procedure.
- Do not substitute a similarly named port monitor unless the queue and driver are actually designed for that transport.
Microsoft Port Monitors · AddMonitor installation interface · MONITOR_INFO_2 fields
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