Searching for forms by a wild card or a string, shows the forms. However attempts to expand and show a full list of forms does not show any forms there.
When this behavior was seen, use browser's developer tools (press function key F12 on the keyboard and refresh the Catalog page in an attempt to show the forms tab again), an error is seen on the browser console:
ReferenceError: isWhiteListWatcher is not defined
1) Log out of Catalog
2) Empty browser cache
3) Login back to Catalog