Answer
At higher altitude, air pressure is lower than at sea level. Water boils at a temperature lower than $100^{\mathrm{o}}\mathrm{C}.$
If the stove barely succeeds in boiling water at this temperature, it will not generate enough heat to boil it at sea level.
Work Step by Step
It takes less energy for water molecules to escape (from liquid to gas) when the atmospheric pressure is lower.
