Start with simple document and build back up.
When I run into problems with knitting documents, I go back to the simplest hello word document and start adding things back in until it breaks. So start with the simplest document then start adding back in sections until you run into your error. This can tell you what's causing the problem.
Copy-paste instead of screen shots.
I can't actually read anything in the image you posted. Copy pasting into a post is going to be more useful. There's some formatting buttons in the edtior for posts. I recommend using the "preformatted text" for pasted error messages, output, and code. The button is an icon representation of</>