If your Screenwriter 6.5 About Box and splash screen says that your serial number isn't available, don't worry! The display of the serial number in Screenwriter 6.5 is purely for YOUR reference -- it doesn't have any effect on your actual licensing.
Usually, the problem is caused when our installer can't access a folder that it should have permissions to write into.
But you can FIX this problem yourself, if you feel comfortable doing so.
FIRST -- open a support ticket and tell us your serial number isn't displaying in the About Box or Splash screen. We will reply and send you a new file to download.
Once you have that file, follow the instructions, below:
1) In the Finder, select the GO > Go to Folder… menu command. Enter this path:
2) drag that file I sent you to the /Library/Preferences folder you just opened. You will get a warning about overwriting the file -- that's OK. You may also be asked to provide your account and password for your computer, because you are moving a file into a normally restricted location.
3) After you do that, re-launch Screenwriter and see if your serial number now shows up.