https://kb.juniper.net/InfoCenter/index?page=content&id=KB4113&actp=search is the KB to configure adress, use doamin instead of IP.
Also, make sure you have dns server ip configured/reachable from the firewall so firewall could resolve the domain of adress.
If policy is still grayed out then check KB https://kb.juniper.net/InfoCenter/index?page=content&id=KB13223&smlogin=true&actp=search matching the same issue.
Thanks,
Vikas