Your Roomba may be experiencing an issue where the battery is deeply discharged and may need to charge longer than the standard 3 hours. (or 7 hours if you have a standard charger)
Even with the charging light showing green (this indicates a fully charged battery) the robot is still charging. If your Roomba exhibits behavior where it charges for a short time then runs for a short time you will need to do the following.
1. Plug the charger into Roomba (if you have a home base be sure to plug directly into Roomba instead of using the home base, this will ensure the robot's charging cycle is not interrupted.)
2. After the Roomba's charging indicator goes to solid green please keep the Roomba on the charger for an additional 72 hours. (3 days)
3. After the 72 hours (3 days) has passed, turn your Roomba on and begin a normal cleaning cycle. If this works successfully it may take several uses for the battery to get back up to the performance it once had.
If this does not correct the problem, please call customer support at 877-855-8593