How do I index all the content with the search_api module? I am using the Search API module with Search API Solr. When I visit my index page at http://example.com/admin/config/search/search-api/index/my-example-index, I see the "Index Now" button is disabled and inactive. I see "Content (7796/7796 indexed)" for the data source.  However, recent content items are not showing up in my search results.  

At admin/config/search/pages, I see "6% of the site has been indexed. There are 7693 items left to index."  Ok, how do I index the rest?

I know that not all content is indexed, because recent content is not showing up in search results. I don't want to index just 50 or 100 content items at this time. I want to index everything, so all content can show up in search results.
You must click the "Queue all items for reindexing" link that appears below the "Start Indexing Now" fieldset, and then once you run that process, you can return to the index UI (example.com/admin/config/search/search-api/index/my-example-index) and at that point the "Index Now" button is active.