It’s odd that the Simply Exclude plugin was causing the problem as I have been using that plugin for a while and before I moved to the Readme theme. After setting up Readme theme it all tested good.
Thanks, I can see that was the problem and the plugin is inactive. Will play around with it some more to see where the conflicts are happening.
Have created an Admin login and sent details via contact form as requested.
To verify the problem, you will need to set the “Blog” page (https://justinroselt.com/blog/) to the Posts page in reading settings and reload the blog page. Currently no page is set as I am using the latest posts shortcode to display posts.