No gas going to my water heater

Question

Water heater in basement of home. Purchased new approx. 2 years ago. Home is empty and the appliance worked fine until one day I found that the pilot light had gone out. I tried to relight but I'm not getting any gas to the system. I checked the shut-off and it is open. The furnace works fine which is also gas and next to the water heater. What is causing the gas to not get to my system? Thank you.