The shortcode should work as expected.
When you say HTML block I’m not sure which one in specific. Please share screenshot if possible.
I would suggest using the “shortcode” block instead.
Note: If any other shortcode can work, then the shortcode from SRR plugin will also work. Please try if other shortcodes are also working in whichever place you are trying to display the reader. Feel free to share more details for quick resolution.
I see that the shortcode has “fancy characters” for “double quotes” and square brackets.
Not sure if that is causing the issue.
Could you please try and share the following?
1) Copy and paste the example seen in “super rss reader – pro -> example”
2) Edit that example with your feed URL and see if it works.
3) A screenshot of the post editor where the shortcode is inserted
4) The page URL where the shortcode is inserted.