Oh, you did not updated correctly. The instructions for updating are:

- Close Sia completely (In Windows, you have to click close on the system try icon of Sia)
- Replace the old installation with the extracted files form the 1.3.1 version you downloaded
- Open Sia again

In your particular case, as what remains to be updated is the daemon (the core software, not the UI that is up to date) you can update alternatively by going to the Terminal and typing "siac update". This is ok for this case, not the general rule for updating if you are using the UI.

Once updated, you don't have to do anything else for the hardfork: you will be prepared ;-)