On the CT100 the filter reminder is set for 90 days. When the filter reminder light comes on it will stay on for 24 hours and then go out. It will then reset the reminder to 0 and start the count again.
If after 24 hours it does not turn out - Try the following:
Reset the thermostat
If that does not work power down the thermostat for 15 minutes and then power up again.
That should solve the issue.