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.
How can this be resolved?
Sorry to hear of the problem you are having.
Could you please try disabling enabled jetpack modules one by one to see which jetpack module is causing this issue?
In Chrome go to “Tools -> Developer Tools” and in Firefox you can go to “Tools -> Web Developer -> Console”