No answer important
The receiver went silent rather than answering.
In detail
Important to separate from error in analytics: a refusal is a judgement about the sender, a timeout usually is not. Mixing them makes an overloaded receiver look like a reputation problem, and the natural response — slowing down — is right for one and pointless for the other. The stage says which timeout expired, and the seventeen timeouts in the capacity profile say how long the engine waited.