I made some progress on this today. What I need to know:
1. what is your activity retention policy in Admin > General?
2. when was this catalog created? (you can query select * from catalog on the vCD DB)
if the create date is older than the retention policy, this status may show as 'unknown'.
The 'unknown' is a status based on querying old jobs for the creation status ... if it's older than 90 days (by default in vCD) then this might show as unknown.
even though it's called 'unknown' the status doesn't seem to mean anything, other than being ugly in the GUI.