Any time you notice any major changes in your SEO stats, indexing, or crawler behavior, start troubleshooting by asking these questions:
- Did you read the Google FAQs for indexing, crawling, and ranking?
- Is your robots.txt file still accessible and were there any changes to it?
- Is your sitemap testing without errors?
- Did you adjust your Googlebot crawl rate?
- Have you had Google's "URL Inspection Tool" to check for errors and request reindexing the URLs?
We recommend exploring Google's Webmaster Tools if you're experiencing issues. Their "Fetch as Google" tool article and their article on troubleshooting sitemap errors offer specific help for debugging Googlebot crawl stats in this situation. Google also includes an entire section in their tools documentation on getting additional support if you're experiencing trouble.
Our debugging articles contain a variety of troubleshooting tips.