This is the service mode switch, which is typically not necessary for common issues like yours. It is mainly used when formatting the ROM or cleaning the mE region for BIOS purposes. It's unlikely that this is related to the problem you're trying to resolve. If your laptop is not detecting AC power, check the Vbus_AC detector and the DCIN_ACOK. Also, verify the power around the BQ24777, including VCC, ACDET, and ACOK. Additionally, inspect PQ304 and PR327