Hello! I have had this problem for a few days now and I think it has something to do with not having many friends in my list (1 to be exact). The website tells me that I need to select a friend even though Ive sent challenges and selected people before. After adding a new person to my list the new person works just fine but the original person I still cant send one too. After requesting to friend them again and removing them from my list of friends I can't send challenges to the only friend I have now.