In your My Games folder you can right-click the FFXIV folder and select Properties, then click on the Security tab, make sure everything but Special Permissions has a Check-mark next to the name, also check the files .CFG inside the FFXIV have the same Permissions as the Folder.

For example, it will say SYSTEM, and in the box below it'll have Read (Checked), Write (Checked) etc.

Also make sure while looking on the Properties' Security tab that ADMIN and your PC username has the same options Checked, if not click the Edit button above the box and turn them on.

They all need "Allow" to be Checked.