/feed/ url showing 404 on each post on custom_post_type product

Hi,

I wonder if this is bugs or not, but I have problem with my /feed/ url for each post on my website.
for example, I have kids-clothes category, with kids have winter-coats-from-xyz and summer-shirts-from-xyz.
The url will be :
https://www.mysite.com/product/winter-coats-from-xyz/feed/
https://www.mysite.com/product/summer-shirts-from-xyz/feed/

For now, It will be showing 404 not found. But the /feed/ url is working for the category, let’s say https://www.mysite.com/product-category/kids-clothes/feed/ , so it’s not working for each post on product-category, but working on product-category page.

Before, I realized that my homepage is showing the same 404 not found when try to get /feed/ lets say https://www.mysite.com/feed/ , But finally I could make it working on my homepage with simple code from >> https://core.trac.wordpress.org/ticket/12943.
I also try to clear my permalinks cache but still not working. Has anybody else got the same trouble as me?

For additional information, I am only showing recent listings layout on my homepage, and running it on latest nginx webserver with permalinks rewrite conf. But I dont have any problem with another wordpress site running on same machine.