I am having the same problem. However, I think the issue is specifically coming from the redirects between the steam mobile app back to the companion app. I am constantly having the same loop issue and unable to sign into it on my phone which has the companion app and the steam app. However, when I sign into the companion app on my iPad (which does not have the steam app), the loop does not happen and I am allowed to sign in. I believe there is some sort of loop error with the companion app when it uses the steam mobile app for authorization rather than it all through safari on the destiny companion app. Hope this helps narrow down the issue. Thanks! EDIT: In case you did not see my other comment for a tentative fix: TENTATIVE FIX: To avoid this loop between the steam app and companion app, when you press sign in on the companion app and it brings up the page to select your platform. HOLD down on the steam option. It will pop out a preview screen of the steam website. Just click on the username part of the preview screen and it will allow you do do the sign in from the steam website while still on the companion app. After you sign into your steam account on the website, you can go open the steam app separately and confirm the sign in. Return to the companion app and approve the account link. This should allow the sign in to work. At least it did for me. Hope it helps!