After upgrading to Server versions 8.12 or 8.13, the Publishers page under Rules > Software Rules > Publishers > displays no certificates in the 'All Certificates For This Publisher' section
This issue is currently under investigation (Tracking: EPCB-25366).
Note: The impact is purely cosmetic. The underlying certificates remain intact and active but are failing to render in the user interface.
Certificates for every Publisher can still be viewed by going to Assets > Certificates > Add Filter > Publisher is: PublisherName (e.g. Microsoft Corporation) > Apply
This issue will be resolved in an upcoming server release.