That message is not necessarily indicative of an issue with the board or footpad. Usually, that message is thrown because the rider is favoring one side of the pad while riding above 2 mph. The board is designed to stay engaged even if pressure is only detected on one side of the sensor while moving over 2 mph to account for riders leaning hard to carve.
In order to help you make better contact with the sensors, we have attached reference photos for where the sensors are under the griptape, this way you can visualize where to distribute your weight to make sure you are providing good contact. Changing your foot placement or the type of shoe you are wearing can create better weight distribution within the sensor and stop that alert from occurring in the app.