The valve is turned on but no water is coming through and into the tank. I've turned it off the back on. I've messed with the valve in the tank that did nothing. What could be causing this?

Hi Lisa

Turn the water shut off valve to the off position and then disconnect the, most likely, braided/flexible supply tube from the shut off valve to the fill valve of the toilet and then direct this flexible tube into a bucket and turn the water shut off back on. If water sprays from the water supply tube then the issue is up in the FILL VALVE... usually a quick fix, so that is good news! If water doesn't come from the supply tube when you turn the water back on then the issue is at the shut off valve.

Report back with your observations and we can tell you the next steps involved, OK? Please include a toilet brand name and approximate age of the toilet...;)

Mark