Republican Secretary of State Scott Gessler urged those people Wednesday to verify their status and register again if they don't show up on the system.
The glitch only affected 779 people who tried to register to vote with a mobile device during those days in September.
Gessler says his office is trying to identify who those people are but they haven't been able to. He says the glitch happened because of a software fix for the online voter registration website.
Gessler says people affected could also still vote with an emergency registration process.
People can check their registration at www.govotecolorado.com.
(Copyright 2012 by The Associated Press. All Rights Reserved.)