Some folks reported issues with this flow earlier today. The reports came in within a single hour period, so I suspect transient network issues.
I spent some time looking at the code here that handles talking to the relay server, and one potential risk here is that if there's an error after the URL redirect occurs, we'll never retry that step. Probably a good idea to reset this, so that if a retry is necessitated after a URL redirect, we can retry the process from the start (including redoing the URL redirect).
Depends on D13580