HEAT CABLE UP THE GUTTER NOT WORKING

[Arthur D.]

Tenant called. Slow drip from ceiling in kitchen. I have a flat roof and 14" of snow just fell. Update: got snow off the roof, all gutters were frozen solid. I have a cable plugged in the garage and then snaked through the gutters. Cable didn't prevent the gutters from freezing. It's just plugged in year round no switch. I really don't know anything about heating cable or how to trouble shoot them. I would like it to work for next winter. Should there be switch , is it tide to a breaker or is it just plugged in like a extension cord ?