if a gas grill's push-button battery-operated igniter is clicking, but grill doesn't light
Follow the wire from the button to where it ends, somewhere near the burner.

In theory, it will be clipped a specific distance from the burner so that a spark will jump between it and the burner to ignite the gas.

In practice, it could be covered with food drippings or could have become detached from where it is supposed to be, or it could be thoroughly corroded.

If you can clean it and make sure it is attached in the right place, it should work okay again.

But more likely there's not much you can do that will make a permanent fix, and you'll end up using a hand-lighter to ignite the flame.