Apparently, there's an issue with Xbox One preventing some users from seeing their friends activity. Don't worry though, Microsoft is aware of the problem and working on a fix.
"Having difficulty viewing activity in your Friends list? Hang in there, we’ve got you covered," Xbox support acknowledged. Thanks for your patience while we work."
According to the Xbox One support page, the issue affects managing your friends list and tracking what friends are doing. There also some problems being experienced when purchasing content from the Marketplace.
We will keep you updated as Microsoft shares more information.