The latest client (v1.0 and up) enables IPv6 leak protection automatically and does not need to be disabled. Due to a more aggressive IPv6 block, disabling IPv6 will actually result in connection issues with the PIA app.
If you are using the legacy client, you can disable IPv6 traffic using the following instructions:
- Go to Apple - > System Preferences -> Network
- Select the first network connection you see listed on the left-hand side, then click the Advanced button.
- Go to the TCP/IP tab at the top
- Beside "Configure IPv6", set it to "Link-local Only"
- Click Ok to apply the change
- Repeat steps 2-5 for any remaining network connections you see in your Network window.
- Reboot your computer, so all changes fully take effect.