You mentioned
Last week the Thermocouple
Not possible as it uses a thermo-pile.Thermocouple makes about 50 millivolts where a thermopile makes 750 millivolts. Easily measured before one replaces it. Connected to the gas valve you should see above 400 under load.
Â
High limit is probable, but not the only possibility. Use you DVOM to troubleshoot before replacing parts. Electrical contacts, gas supply, and pilot flame all have a effect on this.Â
Â
Some high limits have to be reset. Like these
So if it tripped, was it in a high setting or was the thermostat off. A good tech would take the time to measure the calibration and test the thermostat.