Here are the steps on how to whitelist a domain to disable the captcha check: (I use google.com here for demonstration, so you need to replace google.com here with the domain that you wish to whitelist)
1- Run the following command to whitelist the domain:
imunify360-agent whitelist domain add google.com
2- Confirm from the command line that the domain is indeed added:
imunify360-agent whitelist domain list
google.com
3- Confirm that the right configuration file has been modified:
grep -Eiv "(^#.*|^$)" /etc/imunify360-webshield/whitelisted-domains.conf | grep -Ei google.com
google.com 1;
https://docs.imunify360.com/webshield/#verification
Note: For this to work the Webshield service needs to be enabled. You can run the following command to confirm if that service is enabled:
systemctl status imunify360-webshield.service
If it's not, then you can turn on the WebShield service via WHM >> Plugins >> Imunify360 >> Settings >> General >> WebShield-Enable.