Hi there.
First things first. Have you checked that the headlight bulb isn't blown?
Sorry, but you're not 100% clear. Is it just the headlight that doesn't come on, or are you having problems starting the engine by way of the starter button? Does the rear light come on? There are so many vaguaries in your report that you'll have to give us ALL the details before we can help you.
BTW, you say that you replaced the solenoid, but it still doesn't work. Why did you replace it without checking the old one, to see if the problem was there? I'm afraid (without trying to cause offence) that you don't seem to have a very logical approach to fault finding. Do you think you're actually up to solving the problem, or do you think you should leave it to someone with more experience?