A recurring startup display requires supply and power-base checks.
If a TH115 repeatedly shows its startup display or restarts, record the exact display, complete thermostat/power-base model and when it happens. A recurring reboot is different from the normal heating-power indicator or a one-time restart after loss of power.
With the circuit isolated, a qualified electrician should verify the control module is correctly seated on its compatible power base and inspect its connections for damage. The TH115 and PB112 installation instructions require the correct LINE/LOAD connections and supply rating.
The electrician should check the supply and connections before concluding the thermostat has failed. Any live test requires appropriate precautions. Do not disconnect protective grounds, bypass GFCI protection or substitute an unmatched power base to keep the heater running.
If correct supply and assembly do not resolve the restart, contact WarmlyYours with the full model, display sequence and test results for the correct service or replacement decision. A countdown alone does not identify a failed heating cable.
Sources: TH115-AF-GA guide and TH114/PB112 installation instructions.