DIAGNOSIS This alert is triggered by the built-in humidity sensor in the Ecobee itself, and it's detecting high moisture levels right there on your wall. This is a warning that the air around the thermostat is too damp, which could lead to mold or damage. It often happens if the thermostat is in a poorly ventilated hallway, near a bathroom, or if your whole house humidity is very high.
FIX First, don't panic—it's a sensor alert, not a command to your equipment. 1) Verify the reading. Go to the main screen on the thermostat and see what the humidity % says. Anything consistently over 60% is in the 'High' zone. 2) Improve local airflow. Make sure no furniture is blocking vents near the thermostat. 3) Address whole-house humidity. Run your AC more, as cooling naturally dehumidifies. If it's winter, high humidity might mean your house is too sealed up; consider running the bathroom fans longer after showers.
IF THAT DIDN'T WORK You can adjust the alert threshold or turn it off if it's a false alarm from a bad location. On the thermostat, go to Menu > Settings > Alerts. Find the 'Indoor Humidity' alert. You can change the threshold to a higher percentage or disable it entirely. Just remember, if you disable it, you lose a useful warning sign.
HEADS UP This alert is separate from the 'Overcooling to Dehumidify' feature. That feature makes your AC run longer to pull more water from the air. The 'high humidity' alert is just telling you there's a potential problem in the environment.