I've sent support questions to both Garmin and Strava but trying my luck here as I'm sure others have encountered this (100% reproducible).
I am trying to link my Garmin Connect and Strava. In Strava, you do this though social media settings and authorizing Garmin Connect. This pops up another browser window that opens the Garmin Connect site (https://connect.garmin.com/modern/oauthConfirm?hl=en_US&oauth_token=022c5e1a-03ca-4f0b-86e2-66d838a2014f&oauth_callback=https://www.strava.com/oauth/garmin_connect/authorize). This window displays the 'Connect powered by Garmin' then 'Strava do you authorizes Strave to use your Garmin account and its data' etc. But near the bottom, just beneath 'Don't have an account? Create One' there is a spinning circle that spins indefinite (>50 minutes). I've tried numerous times with the same result every time. I've even tried changing my Garmin account to the same email address used by my Strava account and still no difference.
Ideas?
For me, this is totally non functional full stop. The Strava integration functionality is perhaps the #1 most important feature to me with the Edge 520.