drupal sitemap error Incorrect http header content-type: "text/html; charset=UTF-8" (expected: "application/xml")

I am looking for help addressing an issue I am having with my Drupal 7 website. I am encountering an error with the sitemap where the incorrect http header content-type "text/html; charset=UTF-8" is being used (expected: "application/xml"). I have attempted to address the issue using standard methods but have not been able to solve it. I am now looking for additional help from a skilled Drupal developer who can identify and fix this issue. If you are experienced in Drupal development, I would love to hear from you about how you can help. Thanks for your time and I look forward to working with you!