I think the OP means that the on-off switch doesn't feel like it's switching (the lever or rocker is loose and doesn't snap into position, say), while the high-low switch clicks properly but has no apparent effect because the system as a whole is stuck off.
From the description, it sure sounds to me like the switch simply broke or wore out and needs to be replaced. It should be a pretty straightforward and inexpensive thing to fix. It would also be quite straightforward to check with an ohmmeter as ivylog mentioned.