Our site completely disappeared from Bing

We completely rebuilt our website about two months ago due to some internal disagreements with the previous agency we worked with. We started working with a new agency which started working on the site in the middle of June. They completely built it in a staging ground before transfering to the main URL, and to my best knowledge they followed all the best practices regarding link redirecting, but we still took a bit of a hit on Google, losing about 30 % of the traffic in the first month, but we are gradually climbing back. The problem, however, is that we COMPLETELY disappeared from Bing. And I mean completely. Even for branded searches we are nowhere to be found. The only way to get to our website through Bing is by writing our website's url directly into the top bar. And the even bigger, I would say our main problem is that no one knows why. We pointed it out to the agency as soon as we figured it out, which was about a week after the transfer (it took a while because only one person in our team uses Bing, and that person seldom goes online), but even they had no idea what happened. They submitted our URL to the Bing webmaster tools, and they even contacted Bing support, but to no avail. It's interesting because the problem only occurs on Bing. It's been more than 2 months now and we're really getting worried there might be some deeper issues with our site. Does anyone have any experience with similar problems and has any recommendations? Any help would be greatly appreciated! Ps: We went from the previous custom solution to now using Woocommerce