If you do not enter the required fields, as Sir Williams mentioned, you will get an error notice and you will not be able to add the record.
Have you entered that basic information, clicked "add", and it still won't add or give you an error message? I have noticed that a few times, too, Maci, when I opened more than one window in my browser. You cannot open two windows to add more than one relative to the same person at one time. I tried to do this so I could enter both parents and add the same marriage record and census record to both at once. I could save the first record, but when I tried to add the second record it just returned to the screen - no error message or explanation.