Technician found that the upstairs outdoor unit king valve was not 100% open. Causing the system to notice the restriction, throwing the low, refrigerant code. Technician also inspected multiple other points of the system, including solder joints, and Schrader valves, etc. System is now operating properly. Homeowner noticed that the downstairs feels cooler in some areas than others so the technician recommends operating the furnace blower at a low/medium low continuous function. This will help circulate air in between operating cycles leading to the main level temperature being more even throughout.