Cloudflare has completely corrected the underlying issue, so this incident has been resolved.
Monitoring · UTC
Cloudflare appears to have mitigated the issue on their end. Mobile users should now be able to sign in.
We are continuing to monitor the situation and will provide additional updates if needed.
Identified · UTC
Due to an issue with Cloudflare, one of our upstream cloud providers, mobile users are currently unable to sign-in. We are monitoring this incident and will provide updates as they become available.