Cause
The preview expired (it lives 5 minutes). Repeating it with the same idempotency key does not extend it.
What to do
Request a new preview with another Idempotency-Key and use its digest.
application/problem+json
{
"type": "https://masnet.com/developers/errors/preview_expired",
"title": "Preview expired",
"status": 409,
"detail": "...",
"code": "preview_expired",
"correlation_id": "..."
}