When upgrading your pfSense installation to version 2.4 follow the below steps to ensure your DNSthingy continues to function.
Access the web UI of your pfSense system directly by IP address. For example https://192.168.1.1:20443
After logging in, go to System / Package Manager
If there is an update available for the dnsthingy package go ahead and install it.
Connect to your pfSense system using SSH or the console port.
Select option 13 to “Update from console”
This process will automatically update the dnsthingy package and reboot the system.