About two months ago my site dropped off Bing as well. Indexing and ranking fine on Google. But it went from having thousands of pages indexed on Bing to having 0.

I have no errors showing in Bing Webmaster Tools and there are no manual actions as far as I can tell. I submitted a report ticket and didn't hear back after 2 weeks. I submitted another to follow up and haven't heard back for 3 weeks now.

Instead of indexing my site, Bing appears to be indexing multiple IP addresses instead. I haven't changed anything within my DNS records so I'm not sure why this would have suddenly happened.