IBCM Link can't be configured, error Cannot retrieve IBCM Proxy certificate. Rpc transport error: status = 8, The underlying connection was closed: The connection was closed is thrown:
PMM Proxy can't connect to the IBCM Proxy over the service port.
You can verify it using PowerShell command Test-NetConnection IBCM_hostname -Port ServicePort
It must return TcpTestSucceeded : True, otherwise, the connection is blocked.
Adjust firewall settings to allow incoming TCP connections from PMM Proxy to IBCM Proxy over the service port.