This has happened on two systems I run. Both started doing this somewhere around U3.1 or U4. Both systems show a version for the first two iXsystems plugins (Asigra & Iconik) and then nothing for the rest of the iXsystems or community plugins. Refreshing doesn't seem to help.
Both system were originally running 11 and were upgraded to 12 when U1 was released. After the upgrade to 12 they were initially OK and it was only on a later upgrade that the version numbers started to go missing.