Unable to open Word Doc

Help, when I try to open a doc in the Word app on my iPhone I get a message in the screen that says “Unsupported server-

Information you exchange with this site cannot be viewed or changed by others. However, there is a problem with this Web site's security certificate.”. I don’t know if this is a question for Apple but I thought I’d ask here first. If anyone knows why this is, I’d greatly appreciate help. 
Thanks!