Sitemap Issue with Yoast and W3 Total Cache

So here’s the issue.

I deleted W3 Total Cache plugin. Yoast generates the sitemap, but I get this error when I try to access the sitemap_index.html.

This page contains the following errors:

error on line 2 at column 6: XML declaration allowed only at the start of the document
Below is a rendering of the page up to the first error.

There is no empty space after the closing tag in my functions.php file. The issue is with something that w3 total cache did to the site. I just don’t know where to find it. Earlier when I had deactivated w3 total cache the sitemap would work. Now, after deleting the program the sitemap is not being generated by Yoast. After searching what I should do I haven’t been able to find anything. Thanks for your help.