What if my TH115 floor heating thermostat is not turning on?

The first items on the checklist would be to ensure that the breaker is on and that power is being supplied to the unit. This can be done by a qualified individual with a volt-meter. Upon confirmation of power being supplied to the thermostat and the device is still not operational; it could be that the unit needs replacing. Call Warmup or your local retailer for a replacement.