If you aren’t receiving input signal to Sensory Percussion, here are the things you should check:
Your sensor/s are plugged in and phantom-power (48V) is turned on and is successfully supplying power to them (the light underneath the sensor’s head will be turned on). Also, make sure that all pads are off on your interface. Now, when you strike the drum, does the input monitor on your interface light up? If so, then proceed to step 2. If not, the problem may be with your interface or with your audio cable, so check to make sure that both are functioning correctly.
Have you added drum models to the instrument tracks? Click the triangle on the model tab to add a drum to be trained for each track. Until you train the drums, you won’t be able hear sound, but once a model is added, you will be able to see input registering on the drum tracks when you strike the drums. See Adding a new drum and training for more details.
If you have completed step 2, but there is still no audio coming into Sensory Percussion, click on the Audio/MIDI button in Sensory Percussion and make sure that your input and output correspond to the interface that you are using. See section Audio I/O settings. If your interface is not appearing inside Sensory Percussion, go to the manufacturer’s website and download the software drivers for the interface.
Are you running macOS Mojave (version 10.14)? With Mojave, they've added security features for controlling which apps have access to certain resources. Sensory Percussion needs access to audio input resources. Check the following setting to make sure Sensory Percussion has access: System Preferences > Security and Privacy > Privacy > Microphone > Allow Sensory Percussion access
If it's only one channel that isn’t registering audio, it could be a faulty cable or channel on your interface. Swap the cable and channel that your sensor is plugged into and see if signal appears when you strike the drum.