Optimize your site according to the Bing Webmaster guidelines, remove duplicate contents, remove unnecessary scripts, plugins, sidebars, ads, links, etc from your site and submit your site again to review by Bing Webmaster Support Team. Use this link to contact Bing or to submit your site to review.
My site suddenly disappeared from Bing search results on September 2020 and now there are no ways to index it back. Because the Bing webmaster support is full of as.h…ls. They not even checked my website after contacting and just provide a copy-paste reply. One said to me that my site is in spam list (which is impossible), another said it doesn’t meet the Bing webmaster requirements, another supprt member asked me to wait 1 or 2 months to index it back.