GatewayTimeout

Andromeda answers 504 with the problem type https://uri.etsi.org/ngsi-ld/errors/GatewayTimeout. The request went to one context source, and that source didn't answer in time. Nothing came back, not even an error, so there is nothing to pass through. The specification sets 504 for a sole source that doesn't answer in time but names no error type for it, so GatewayTimeout is Andromeda's own name. See Andromeda's own types.

When this comes back

An exclusive or redirect registration makes one source the only holder of a resource, and that source doesn't answer within its timeout. Check that the source is up, and that its management.timeout gives it the time it needs. See When the one source fails and Sources that fail.

In a batch, the failure is reported against the entity that hit it in a 207 instead.

A 504 from Andromeda itself, with no source involved, is a different case. It means a remote @context couldn't be fetched, and its type is LdContextNotAvailable.