Upon inspection I see an error in my browser's console. It seems like you've a third party plugin Layer Animation installed, which is breaking the Revolution Slider plugin. Please deactivate it. If this doesn't help then test for a plugin conflict. You can do this by deactivating all third party plugins, and seeing if the problem remains. If it's fixed, you'll know a plugin caused the problem, and you can narrow down which one by reactivating them one at a time.
Also clear all caches including browser cache then deactivate your caching plugin and other optimization plugins. If you're using a CDN, please clear the CDN's cache and disable optimization services.
Let us know how this goes!