The MAX drop on the "LDO" is 1.2V which would make a 4.2V fully charged LiPo 2.9V. Try using a MCP1826-33 with appropriate capacitors, resistors and if you want to prevent low voltage and draining the battery too far, put a KA75330 on the output and shdn pin (MSC1826-33). Do not plug in to the USB p...