I was having the same problem and after 5 days finally got the message to load. Here is a copy of the message.
The police certificate required for COUNTRY is not needed in order for the interview to be scheduled. However, the police certificate must be obtained and uploaded before the visa interview. Please use our Document Finder athttps://nvc.state.gov/findfor acceptable documents guidelines.
Message, DS-260 Review note
in National Visa Center (Dept of State)
Posted
I was having the same problem and after 5 days finally got the message to load. Here is a copy of the message.