My friend has a myson 325 thermostatic on demand hot water heater, we got the pilot light to work but nothing else will ignite,so she doesn't,t get any hot water from it can you help me help her?

http://www.asapheat.com/mysonparts.htm

It has a mercury thermostat sensing bulb on it. Its not uncommon for parts to stick. You may want to tap on the thermostat body to get the bellows moving.