The click does not work properly

The click does not work, Im not sure why this occurs. In the video Im always clicking but when I aim to the site between the slab and the iron trapdoor the click does not work. (I cant upload it because it exceeds the max amount of MB [10 MB])
Link of the video: https://www.youtube.com/watch?v=3bXJ4PMQ1_4&feature=youtu.be