Hello,
Thanks for contacting us.
Please know that the images are already included in your sitemap.
You can open your post or pages sitemap and see the images beside each post’s URL: https://i.rankmath.com/3t6KjL
The option you are referencing pertains to the attachment pages. We do not recommend enabling attachments, let alone have a separate sitemap for it. The reason being that attachments cause thin content issues and dilute down your website’s authority.
Here’s an article on the topic: https://www.seoblog.com/2018/04/wordpress-attachment-hurt-seo/
Hope this helps. Let us know if you need any further assistance.
If you search site:muthusblog.com and search on images you will find just one image but there are more than 40 that aren’t showing that’s the problem.
Hello,
Have you enabled the option to include images in your sitemap in Rank math > Sitemap Settings?

After doing so, remove all your sitemaps from Google Search Console and re-submit your sitemap_index.xml.
Let me know how it goes. Looking forward to helping you. Thank you.
Yes, I have already enabled that option, Jeremy. The problem is everything gets indexed except for the images. https://muthusblog.com/attachment-sitemap.xml This link contains no URLs for my images.
Hello,
Thank you for the update, and sorry for the delay.
There could be a number of reasons why Google has decided not to index those images and include them in the image search.
1. You are not using original images.
2. Your post is relatively new and it will take Google time.
I’ve checked one of your posts, and since that post is indexed already, Google is already seeing those images so there is no question of Google not seeing the images. It is just a matter of Google choosing not to rank or include the images in their search results.

I hope that helps. Thank you, and please don’t hesitate to contact us anytime if you need further assistance.
Most of the images used are either original or created via infographics. The attachment sitemap has 0 URLs could that be the issue? 
Hello,
O URLs in the attachment sitemap is not the issue as images are already included in your posts/pages sitemaps.
As my colleague mentioned in the previous message, one of your posts is indexed already, Google is already seeing those images. And it’s totally up to them if they include your other images or not.
You can also try resubmitting your sitemap on Google Search Console.
Hope this helps. Let us know if you need any further assistance.
Ok, Thank you and everyone at Rankmath Support. I’ll try resubmitting the sitemaps on search console.
Hello,
Thanks for getting back.
Please don’t hesitate to contact us if you need assistance with anything else.
Hello,
Since we did not hear back from you for 15 days, we are assuming that you found the solution. We are closing this support ticket.
If you still need assistance or any other help, please feel free to open a new support ticket, and we will be more than happy to assist.
Thank you.