There is a possible race condition in the console operator where the managed cluster config gets updated after the console deployment and doesn't trigger a rollout. 

4.10

Rarely

1. Enable multicluster tech preview by adding TechPreviewNoUpgrade featureSet to FeatureGate config. (NOTE THIS ACTION IS IRREVERSIBLE AND WILL MAKE THE CLUSTER UNUPGRADEABLE AND UNSUPPORTED) 
2. Install ACM 2.5+
3. Import a managed cluster using either the ACM console or the CLI
4. Once that managed cluster is showing in the cluster dropdown, import a second managed cluster 

Sometimes the second managed cluster will never show up in the cluster dropdown

The second managed cluster eventually shows up in the cluster dropdown after a page refresh