Changing the main picture of a group

Hi,I'm the administrator of the group Australian Nude Places. The main picture of the group came up as the first approved picture uploaded by a member. Does anyone else know how to change the main picture of the group? This should be a straight forward preference of the group settings.
I sent this question to True Nudists help in the contact us page. It created a ticket number which I got an email for. Straight after I got another email that the ticket had been closed. The link in the email goes to a 404 page not found. This is very poor customer service.
Regards,Nudyjay