Is the water level dropping when it cycles fresh mat in? What's your advance length? Do you use the media basket? If so, when was the media last changed?
Your sensor is installed incorrectly. Your sensor needs to be flipped, so that high water is detected outside the roller. You may need to disconnect and flip the body for the sensor to be installed correctly.
It should only say high water if the water is actually hitting all 4 prongs or the sensor is incorrectly installed.
In the app, make sure you also correctly specify what side it's installed as well so it reads the correct pair of prongs