"The CSR was rejected by the server Node" error that results in not being able to trust a node

"The CSR was rejected by the server Node" error that results in not being able to trust a node

When trying to trust a node, we may see the following error and the node cannot be trusted:

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 nodemanager.trust.CertificateMonitor: The CSR was rejected by the server Node [serverId=c8ca80cb-752f-4918-b1bb-46d273a292e5, serverName=<server name>, port=9443, online=true, siteID=5c2c7b84-e1f4-4187-9799-85a2a48f0ebc]. It may already have a CSR for this node.
======== The reason for this behavior is that the nodemanager.properties may have incorrect backend communication port information for the Spotfire Server. The registration port may however be correct which is why the node appears in the untrusted nodes tab. 

To resolve the issue, update the nodemanager.properties file with the correct backend communication port that was used during the installation.