The group list does not appear to show all the groups. One has to tab between the sorting options and hope that the desired group will show up in the top groups in the list. There should be a way to scroll through to see all groups.
This should work.
One can access all the groups from the “Menu” then “All Groups”.
The Groups widget at the right only shows the eight most recently active public groups. (Private and hidden groups do not appear there.) It is like “Recent Posts” and “Recent Comments”—a pointer to current activity, not a comprehensive list of groups.
You can see all public groups by using the menu at the top right and selecting Groups/All Groups. This will show a list of all public groups broken into pages. (We don’t currently have more than one page of public groups.) You can sort the list of groups in a variety of ways.
The Groups/My Groups item in that menu will show all groups of which you are a member, including private and hidden groups.