This URL accepts the POST request + various parameters, (but not the GET) … so you see the error.
In any case, this URL should not be accessible to Google
So you can exclude it this /robots.txt Adding the code
Disallow: /widgets/Listing/ajaxListing
And just in case, check the pagination in the categories.
And it looks like you are using an incorrect address for the site map /sitemap\_index.xml This works /sitemap.xml