The issue is that my keywords are listed (IPTC) in the box but when I click "Add", nothing happens. Is this an issue only for me or are others having the same problem? Even if I delete all the keywords and then paste/type them in the "Add" button still does not function.
There's sometimes a bit of a delay whilst FT's system 'catches up'. When it happens just click Back to the My Uploads page, leave it a few seconds and then try again (preferably with a different file this time).
Just make sure that you leave it a good few seconds after you've clicked a new file to Edit before you hit the Add button to transfer the keywords. The indicator bar (going to fully green) at the bottom of the page is a useful tool for ensuring that the system is ready for editing to begin.