Cookpad Senior Web Developer/Software Engineer interview questions

It was position in Bristol, the UK that required relocate. First of all the interviewer wrote me on mail and we planned time to first skype-interview. The interviewer was a very friendly and nice person. He told about the company and I told about my experience. However, my English was not good but he helped me to pick a word one time. After it, he told me that the next step is the exercise to refactor some code. When I looked at I thought that it was a very easy exercise. Unfortunately, after their review, they told me that we have not to continue our process. I don't know when I was wrong.