Resolved
The fix has been confirmed. Affected users should now be able to sign in and use SELECT normally.
Monitoring
We have rolled out a fix to the login issues being experienced by some customers and are monitoring the errors.
Identified
Some users are unable to sign in to SELECT. After entering their credentials, they see an error page or are sent back to the login screen. Other users aren't affected, and SELECT's dashboards and data collection are working normally.
We've identified the cause: a recent change to our website infrastructure rejects sign-in requests from accounts with unusually large session data. We've reported the issue to the team that manages it, and a fix is in progress.
We'll post an update when the fix is deployed.