All error codes

interface_not_found

HTTP 404 Network interface not found

What happened

The network interface named in the path is not on this server. The identifier is the slot name, such as net1, and it disappears when that interface is removed.

What to do

Read GET /v1/servers/{id}/interfaces and use a name from that list. A 503 network_config_unavailable on the same path means the interface configuration could not be read, which is not the same as the interface being absent.

Retrying

Repeating this request will not help.

How it arrives

{
    "type": "https://docs.fiberax.com/errors/interface_not_found",
    "title": "Network interface not found",
    "status": 404,
    "code": "interface_not_found",
    "request_id": "a277dcd1ca652c65"
}

Branch your code on code, never on the wording of title.