Customer complaint: No heat. Previous service tech Chris was on-site Monday but could not find an issue as the furnace was operating at that time. Customer reported the furnace stopped working again and displayed an "Ignition Loss" error code. Replaced the flame sensor and inspected the furnace for proper operation. Continuously started and restarted the furnace to observe ignition and flame behavior. After multiple test cycles, flames ignited normally each time with no concerns about ignition. Furnace is now operating normally.