A blank and unresponsive thermostat can be caused by several factors. First, check if the batteries need replacing, especially if the thermostat is battery-operated. Dead batteries are a common and easily fixed issue. If replacing the batteries doesn’t solve the problem, inspect the circuit breaker for any tripped switches that might cut power to the thermostat. Loose or damaged wiring can also lead to a blank display, so check for any visible wiring issues. If the thermostat remains unresponsive, it might be malfunctioning or outdated and require replacement. Ensure that the thermostat is compatible with your HVAC system when considering a new one. Persistent issues should be addressed by a professional technician to ensure proper diagnosis and repair.