A:Answer Hello! the self test functions by placing the UPS in to battery mode for a short period of time, if the UPS's batteries are completely depleted his can cause the UPS to shut down. If you have owned the UPS for less than 3 years I would encourage you to reach out to our support at 1.877.297.6937. If you have had it for longer then you may need to purchase a new battery for the UPS, you can find the correct replacement SKU https://www.cyberpowersystems.com/battery-replacement-tool/. To directly answer the question though, hold down the Enter Button for Setup, tab down until you see "dEF", press enter, tap up to "YES", press enter again to factory reset the unit.