Hello,
in the screenshot about your search for unmanaged clients, you can read that the client has not been found as "unmanaged" but as "unknown", it is not the same, hence the issue here is "a managed client is not shown/found in the console".
If as SEP agent is "online" but you don't see it in the console, most common reasons are:
1) the SEP agent is in user mode and your client view is not set to show users
=> try to view/search SEP agents in user mode
2) the hardware ID of that SEP agent is duplicate (did you clone that system?)
=> reset the hardware as explained in a previous post