XML Sitemap Generator 4.0.8 error message

Hello

The plugin did work, now I get the following error message….

<b>This page contains the following errors:

error on line 13 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.</b>

Any ideas?

Gary

https://ww.wp.xz.cn/plugins/google-sitemap-generator/