Did you get such error message while submitting your sitemap to Bing Webmaster Tools?
We encountered an issue when we tried to download this sitemap
You probable is using Yoast SEO plugin.
There are two things to do to solve this issue:
1. Disable sitemap option in Yoast properties
2. Install Google XML Sitemaps plugin
That’s it. All errors should be gone then Bing will read your sitemap next time.