This just started happening recently. I wanted to make some changes to my homepage but when I clicked customise the Theme showed with no Hero Image on my Homepage and neither did I have any access to Widgets, they were simply not showing. Thinking this was a cross Plugin conflict I disabled them one by one to see which was the issue and it turned out to be Jetpack.
Without Jetpack I have no idea of Stats and other features that compliment the WordPress framework and functionality of the site.