Insinkerator SST hot water tank problem

I think I have a faulty tank, but thought I'd post a note here to make sure. My daughter's Insinkerator hot water dispenser is not dispensing any water. I inspected the lines, and there aren't any kinks or leaks. I also removed the tank, drained it and flushed it, and then drained it again. When I hooked it back up, and turned the dispenser handle, I could hear the water running into the tank (in her system, the incoming line goes into the tank through the dispenser valve rather than directly). The tank is also heating when plugged in. But still, no water comes out. Time to replace the tank?