ServiceNow instances have updated to allow only TLS 1.2 and System Center Operations Manager is not able to communicate with ServiceNow anymore.
Release or Environment
All ServiceNow instances
ServiceNow instances have been migrated to support only incoming traffic from TLS 1.2 as the use of TLS 1.2 is a recommended security best practice that provides a higher degree of privacy and data integrity over previous versions and to maintain compliance with NIST 800-53.
Refer to the steps mentioned in the Microsoft documentation below:
In case you need assistance in implementing this, log a case with Microsoft support and they shall be able to assist you on this.