Sundance wireless temp monitor is reading ‘Hi’. Water temp in the tub is set at 102 and that is the reading on the hot tub panel. Is the sensor defective or is the heater on continuously? Suggestions?

Sundance wireless temp monitor is reading ‘Hi’. Water temp in the tub is set at 102 and that is the reading on the hot tub panel. Is the sensor defective or is the heater on continuously? Suggestions?