I'm not getting hot water in the house. What could be the possible reason?

Frozen pipes?
Where do you live and what kind of hot water system do you have?
If you have a tank heater (gas, electric, or oil fired off a boiler), go see if it's on, and feel the pipes coming out of it and follow them, and answer back.

Not enough information. Do you mean you're not getting any water from the hot water taps throughout the house, or do you mean you're getting cold water from them. Also need to know how you heat the water... electric boiler, gas boiler, oil fired boiler, domestic coil... etc.