Hi,
Its either a bad thermal fuse, bad door switch, bad broken belt switch, or bad control board.
Lets check your thermal fuse first, its the most common part for this issue.
Unplug your dryer first before opening it up!
Look here:
Parts for Whirlpool WGD9500TW1: Bulkhead Parts
Your thermistor is #42 located on the top of your blower wheel housing, your thermal fuse is #30 its just on the left of your thermistor.
You would need to take off the lower front access panel under your door, then take off the duct assembly#45, by removing the two #11 screws.
You would ohm the thermal fuse with a
multimeter for continuity to see if its good or bad. Or jump it just to see if your dryer comes on just to test it. Don't run it jumped for a cycle, very dangerous.
You can use an alligator clip to jump it or remove the wires from it and tape them together with electrical tape. Make sure your dryer is Unplugged first before touching the wires, then once you have them taped together, you can plug it back in to see if it turns on.
Here's the thermal fuse for your model you can order, if you need it:
Whirlpool WP3392519 Dryer Thermal Fuse
Watch this video to ohm test your thermal fuse:
<iframe width="496" height="304" src="https://www.youtube.com/embed/3nicyh6EUHc" frameborder="0" allowfullscreen=""></iframe>
Let us know what you find.
Jake