Hi,
Thank you very much for the details, I have checked your configuration and made a quick correction.
Since you only want results from a single category, excluding all the others is not neccessary. The reason why there were no results is, becasuse most of the posts from ‘Tech talks’ were in multiple categories, but because those categories were excluded, the plugin took that as priority and excluded the affected posts as well.
I resolved that, by simply clearing all the exclusions, and left the inclusion of ‘Tech Talks’ in effect: https://i.imgur.com/9sZI2QB.png
Now, you should only get results from post within the ‘Tech Talks’ category. I hope this helps!