This is the issue.
All of your elements (v2 and classic elements) are disabled. I did go ahead and enable just the v2 elements and they are all now showing on the header/footer builder.
You can see the setting under Pro > Settings > Permissions, more about Permissions options here.
I also saw that you disable the Templates, Global Block, Colors, and Fonts features.
Please enable that, you might be needing these features in the future.