Have you tried editing the page outside the Pro Builder? If so, some of the serialized data important in the Pro content might have been lost which is why you are not seeing any content when you try to load the page in the Pro builder. In case you have done the editing outside the builder, you will have to rebuild the page in case you do not have a backup of it.
If you did not edit the page outside the builder, try testing 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.
if the issue persists, please provide us with the admin access to your site in a Secure Note: