post-upgrade to vCloud Director 5.5 - Catalogs' status 'Unknown'

After upgrading from vCD 5.1.0 to 5.5 GA, I noticed that all public Catalogs have the status  'unknown'. Also, some of the dedicated Org-level catalogs are marked as 'unknown'.

What is happening here and can somebody tell me how to fix it?

Btw, I've come across this post with similar problem but at the VM level: https://communities.vmware.com/message/2244735

Thanks in advance for any help.

PD