The issue has been resolved.

An unusually large number of servers failed at the same time. Sirv is designed to continue normal operation during a server outage and all systems did continue as normal, but some file uploads failed.

We are considering what possible changes could be made to assist in such situations in future.

A server fault is causing some file uploads to fail for a limited number of accounts. The issue is being resolved. If you experience failed uploads, please pause and try again later.