Hi Jim: It's possible that the string may have come off the pulley on the end cap. Check to ensure the string is not broken and that that the string has not slipped off the pulley inside of the end cap. If it has, that's your issue. You have to pull off the cap, put it back on the track and put the cap back on. It does take some elbow grease to pull those caps back. If you need help, we can arrange a team to fix the issue. Just call us here at the office.