Description of problem:

Successfully imported cluster to ACM managed hub are moving to 'Unknown' status frequently. Addons are moving to 'Unknown' status and the message shown is, 'Registration agent stopped updating its lease.' In approx 15 mins the cluster is moving to 'Unknown' status

Also have observed that the same method used to import the cluster successfully once does not work again. For example if token and server details are used to import the cluster then with same options re-importing the cluster after detaching is not working.

This issue is faced on the HCI racks as well as the ibm baremetal clusters —
rackm03, rackm14,

Note:  This cluster is a different cluster than where the hcp cluster/acm hub cluster is created.

Version-Release number of selected component (if applicable):

OCP: 4.18.0-rc.5
ACM: 2.13.0-40
MCE: 2.8.0-201

How reproducible: It is happening frequently

Steps to Reproduce:

1. Create a Provider cluster
2. Create hcp cluster 
3. Create ACM hub on the hcp cluster
4. Import a third cluster on the ACM hub

Actual results:

Successfully imported cluster to ACM managed hub are moving to 'Unknown' status frequently. Addons are moving to 'Unknown' status and the message shown is, 'Registration agent stopped updating its lease.'

Expected results:

Successfully imported cluster should remain in imported successfully status.

Additional info:

ibm slack discussion
rh slack discussion