How Does the guitar work lesson

Hello when I was going through the lesson with Lisa on "How does the guitar work" she was shortening the string by holding down at the frets and then plucking but my bass E does not do anything once I hold it down anywhere.... it has no vibration at all as if I cut it off completly. What am I doing wrong?

I figued out what I was doing wrong so diregard.... thanks I was thinking my string wasn't right but it was user error :)