Plot hole: Richard eventually manages to travel back in time by removing all the modern items from his room. But what about the spotlights above his bed? (00:31:40)
Plot hole: The watch that is presented to Collier by Elise which starts this entire story is never purchased, stolen or acquired in any way, but left behind by Collier. It is just there, which is a paradox in itself.
Answer: He was no longer able to put everything out of his mind, which was a requirement to successfully time-travel. He was distraught and unable to focus enough mentally. He stopped eating, and as time went on he became weaker and weaker.