https://vixdeo.com/errors/material-not-ready
The material is still uploading or being verified (its content is hashed and measured before it can be used), so the request was not started and nothing was charged. Repeating the request alone does not move it: `extensions.next` says what does — `complete_upload` with the `handle` of each item in `extensions.items` (it also resumes a verification that nobody is attending) — and `extensions.retryAfterSec` how long to wait before repeating the request.