5010: Media source capacity exhausted.

HTTP status: 503.

The service’s shared capacity for fetching and holding partner-hosted media is fully in use. The send was not accepted and nothing was fetched. No Retry-After is quoted; capacity frees within seconds as other fetches complete.

• Retry the same request shortly.
• Upload the bytes with POST /v1/media and send the returned upload_ref, which does not use fetch capacity.