Had the same problem due to negative SEO campaigns by naughty competitors. Wrote to Bing Webmaster Tools Support team (https://www.bing.com/webmasters/help/webm

Had the same problem due to negative SEO campaigns by naughty competitors. Wrote to Bing Webmaster Tools Support team (https://www.bing.com/webmasters/help/webmaster-support-24ab5ebf https://www.bing.com/webmasters/help/webmaster-support-24ab5...) and after a lengthy process got a response that ”the issue” had been addressed. It’s been a few months since and my website is indeed back in the search results so I advice whoever is having this problem to reach out to Bing.