After upgrading, in `Settings` > `General` you must set `DNS Server Local End Points` to your ynh server's IP address(es) and then scroll to the bottom and `Save Settings` to restart the DNS server.

eg: 
```
192.168.0.88:53
[2981:2cb2:8e86:91f6:4dab:cc4b:2fba:463b]:53
```