[DByers]

Many permanent baseboard heaters will come in 120v flavor, most under 1500watts will be available in 120v but at that size will require its own circuit. A 220v dedicated circuit is preferred, but like in your situation maybe not available. If the heater was small, say 500watt @ 120v then your amps would be just over 4 with a BTU of around 1700. Plenty of heat for a room that size though it may take a little time to warm up the room depending on insulation and where you live.

As suggested, check the breaker box (loadcenter) and be sure nothing has tripped. If he did cut into an existing circuit and you tripped a breaker other things or receptacles should not be functioning.

The heater thermostat could have gone bad, depending on the quality of the unit.

Alot of variables such as bad grounds, loose connections and neutrals could be suspect. If you are not comfortable with diagnosing the problem, hire an electrician or at least have your friend come back and explain how he installed the BB heater.