Did you create a new GUID Partition Table (GPT) as it was suggested above as a possible solution or you just reinstalled the system. If the latter please try the former.
https://gparted.org/display-doc.php?name=help-manual#gparted-create-partition-table
Important If you have several drives on your system, make sure to pick up the one you intend to manipulate from the drop-down menu at top right of Gparted’s window.