missing categories in dropdown menu after update

Hello,

So we just had to do a re-update and now some of the categories in the drop-down menu (the one containing are missing. The pages that were linked to in these categories are also missing now. Any idea where they would have gone? Also, how do we choose which items appear on that menu and find categories that are no longer on that menu?

Here is the link to the category of the website that contains the missing stuff. Note that any link clicked on within this section is missing. They used to be accessible from the dropdown menu on the left, but they aren’t there anymore and I can’t seem to find them. If I did find them, I still dont know how to add them back to that menu and make them accessible again.
https://www.jackkempfoundation.org/kemp-forum/