I disabled all plugins, and I seem to have the same issue. Just a blank panel.
I noticed that the link tied to the Edit button (pencil) only says
javascript:;
while the links on the Clone and Trash buttons are complete:
wp-admin/admin-ajax.php?action=visualizer-clone-chart&nonce=6119545912&chart=458&type=all&tab=settings
I can edit the chart if I copy the Clone URL and change the action to visualizer-edit-chart
I don’t know why the link on that button is not being generated correctly, but the other 2 work fine….
Not a great workaround, but hopefully will help you until we figure what’s going on…