Scrivener support has provided a solution to getting Scrivener working again:
1. Go to System Preferences > Security and Privacy.
2. Choose the last "Privacy" tab.
3. Choose "Contacts" from the list on the left.
4. On the right, where it says "Allow the apps below to access your contacts", un-tick "Scrivener".
Scrivener will then open as normal in Beta 3.
Thank God!
And thank you!