Can’t flush after changing nginx settings

Hallo

I am refferring to your help article here

https://rankmath.com/kb/xml-sitemaps-nginx/#:~:text=Add%20Rewrite%20Rules%20to%20Nginx%20Server

My hosting have added the re write rules.

The sitemap can be seen https://yappily.co.uk/sitemap_index.xml

But Google Search Console will not accept it.

Point 2 of your article is to ‘flush sitemap settings’ but I do not have the option you ask me to change in my dashboard – please see screenshot here https://yappily.co.uk/wp-content/uploads/Screenshot-2023-06-15-at-13.12.43.png

Please tell me how to ‘flush sitemap settings’

Thank you!