There are a couple reasons why a new user might think that their probe is only working on one side-
They are trying to adjust both sides of their toning unit believing the two sets of +\- keys adjust the two sides of their probe. Please note that the +\- keys on the side of your toner that your probe is plugged into control BOTH sides of your probe. The second set of +\- keys is for a second probe and should not be adjusted if you only have one probe attached. The second side of your toner will remain at 0 during your workout or will not go above 10 mA's if you attempt to adjust it without a second probe attached.
The stimulation "feels" like it is only on one side. Internal sensation can be a bit tricky. Some women have altered vaginal sensation due to childbirth and vaginal trauma, as well as normal aging. Sensation will be different for everyone, some women have no sensation and can raise the mA's to the max on any program without feeling the probe conducting or any discomfort. Some women can feel their muscles contracting comfortable by 10 mA's.
To best determine how your probe is conducting you can perform a palm test. You will need to wet your hand under the tap and hold the probe firmly in your hand. Both conducting panels must be in contact with skin. One panel should be pressed to the pad of muscle at the base of your thumb. Turn on your toner by pressing the Power button, press the P button until P01 appears on the screen. Press the waveform button, the one with wavy lines, until the strong waveform appears on the screen. The strong waveform is the wavy line with a square top and square bottom. Now press the + key on the side that your probe is plugged into. When you can feel and see the probe working against the muscle below the thumb you can stop raising the mA's and power the device off. Rotate the probe so that the second panel is pressed to the muscle below the thumb. Press the power button and then press the + key until you feel your probe working against this muscle.
Your probe is designed so that both conductive panels must be sensing full contact with skin to work. The sensor and conductor are the same circuit. If one panel is not sensing then the entire probe will not work. It can never fail on just one side. To test this, power your device on and raise the mA's while holding your probe without touching the metal plates. Your toner will stop at 10 mA's. Now, touch your finger to just one conductive plate. Nothing will happen. When you pinch the probe between two fingers so that one finger is on each plate you will feel current begin to transmit.
Please rest assured that even when you cannot sense your probe working internally that it is still conducting current to both panels. Your muscles will be forced to contract, even in areas where you have altered vaginal sensation. The toner does not rely on sensation to control muscle contractions.