@s1awek, I had the same problem with the website that I maintain. The plugin found a lot of broken links in the comments, but none in the blog posts. What I did, I unchecked the checkboxes “Pages” and “Posts” on the “Look for links in” tab of the plugin settings, clicked the “Save Changes” button, then placed the checks on the checkboxes “Pages” and “Posts” again, and clicked the “Save Changes” button once again. Then I used the Nuclear Option (Re-check all pages). After that the plugin started to find broken links in the blog posts as well. I hope this advice can help you.