OpenDNS's "Dynamic IP" updater is a little opaque. Try using this python script instead, which you can customize for your own needs.
Install required python modules:
pip install -r requirements.txt
Create a config file called config.ini in the same directory:
[Main]
label: YourNetworkLabel
username: your@email.com
password: your-opendns-password-here
Run this to update your IP address:
python update.py
I found that OpenDNS requires that your password contain at least 1 special character. My password contained a couple of these, and it actually caused "HTTP Basic Auth" to break for me. So I changed my password to only contain alphanumeric characters with an underscore as my special character.