eBay has reorganized the Collectibles category, eliminating some of the smaller categories. This likely has caused some of your saved searches to no longer work. If you cannot use the saved searches as a starting point and change the category from there, you may need to create some new searches.
What seems to work for me is to start with a search using keywords -- if you are trying to browse a category and you do not know what keywords to use, try words from the category name. From your search results, try narrowing the category using the links on the left side of the page. Then see what filters are available for that category.
For instance, to search for baseball cards, start searching using the keywords baseball cards. If you are looking for individual cards, try the Single Card category; but you are looking for sets or lots, change the category to either of those. Then take a look at the filters to narrow your search further.
