You can follow the below simple steps to upgrade your Patreon WordPress installation to use API v2, which is required by many advanced features like post sync.
1 - Visit “Patreon settings” menu in your WP admin
2 - Click ‘Connection details’ button
3 - Clear all fields which you can clear, and click Save.
4 - Visit the below page that lists the apps you have at Patreon:
5 - Find the app for your website. You can confirm the app by checking the ‘Redirect uri’ value for the app, visible in app details. The redirect uri that matches your site is the app.
6 - Delete that app.
7 - Go to WP admin at your site, visit “Patreon Settings” menu
8 - Click “Connect” to start connection wizard to reconnect your site to Patreon
When you finish the connection wizard steps, your site will have upgraded to API v2 automatically, and you will be able to use advanced features like post sync.
Note: If you have connected a WordPress site to Patreon api using the setup wizard before, you wont be able to use the setup wizard to connect another site to the api. In such a case you will need to manually create a client at Patreon and copy its details to your site.