Hi Ferreira,
Is this happening for all users or just one? Can you try clicking the gear icon in the right hand side of the tab and see if you can do a "Restore Defaults" (First take a screen shot of anything custom in any of the sections that might appear so they can be added back as needed after the Restore Defaults). Also, is there anything in the drop down arrow next to the section header that may be filtering out anything?
Thanks,
Kristin