Technician Taylor arrived on scene to investigate reports of tankless Navien not working. Client Show technician around to side of home where unit was mounted and plugged into a standard exterior GFCI outlet along with the irrigation system. Technician quickly noticed that the GFCI was not lit up. Technician attempted to reset and was not able to, technician could not fix at the fuse box either. Technician ran extension cord from garage outlet to tankless unit and it fired up immediately. technician deemed problem not to be with Navy and tangless unit but to be with the GFCI outlet. Client stated her ex-husband installed the unit and she would have him come out to take a look at the electrical.