Hi. This is Ali from Fiji. I am a biomedical technician in the Ministry of Health. I received the above mentioned equipment with some issues. I have attached pictures of the equipment. When the suction pads are placed on the patient, there is no tingling effect. The patient cannot feel any stimulation by the equipment. The model of the equipment are: Model: STI-300 Serial: 1916 Could you please assist me with the troubleshooting process? Thanks in advance.