Hi @Tony Gedge ,
Have you followed the SCOM - VMM integration documentation step-by-step?
Integrate VMM with Operations Manager for monitoring and reporting
https://video2.skills-academy.com/en-us/system-center/vmm/monitors-ops-manager?view=sc-vmm-2016
You can also refer to the documentation below which goes deeper into the error 11823:
https://video2.skills-academy.com/en-us/troubleshoot/system-center/vmm/vmm-integration-error-11823
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Best regards,
Leon