When I visit https://my.callofduty.com/friends I get the following:
If you select the "Add Friends via First Party Account" it just opens a new tab/browser window with the same page. My XBL, PSN, Steam, and Battle.net accounts are all linked. I've tried unlinking and re-linking them, but continue to get the same (page) above.
Additionally when I try to access my friends list or friends comparison in the Android app I get the following error:
ERROR Please check your network and try again.
This happens on a stable Wi-Fi connection and cell data.