Check its normal switch position and the exact power-base installation.
Check that the thermostat’s normal switch is in On, and note whether the heating circuit’s breaker or ground-fault protection has tripped. Do not repeatedly reset a circuit that trips again.
If the display remains blank, have a qualified electrician identify the complete TH115/TH114 control and power-base model. With power isolated, check the control is seated correctly, connections are secure and the incoming supply and heater are on the terminals or leads shown by that base’s diagram.
The electrician should verify the rated incoming supply before diagnosing a failed thermostat. Do not group wires only by color or copy positions from a different replacement base. Live-voltage testing requires appropriate electrical safety precautions.
If the supply and correct module/base assembly are confirmed and the display remains blank, obtain a model-specific service or replacement decision. Leave the system off if there is damage, overheating or a recurring protective-device trip.
Sources: TH115-AF-GA guide and TH114/PB112 instructions.