Invalid API key

While not an expert with REST, I've done enough of them to know when something seems broken. No matter what I do I continually get "Invalid API key". I have set and reset the key several times in the admin panel (and saved it). Even when Copying the sample post, it returns the error. Below is my latest attempt and log.
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[17/November/2018 @ 19:49:47] Action/Info: Incoming data received:

{
                "api":"YS9TJ2C78I42N4IHMMPQO3I1HB3NTQ",
                "op": "ticket",
                "tickets": {
                    "ticket": {
                        "name": "Joe Bloggs",
                        "email": "email@example.com",
                        "dept": "3",
                        "subject": "Hello, can you help please?",
                        "comments": "Lorem ipsum dolor sit amet consectetuer tristique leo lacinia orci lorem. Id tempor vitae et congue Nulla vitae gravida ac ipsum odio. Laoreet a euismod et Nunc laoreet Lorem et pellentesque cursus augue. Nec ipsum leo facilisis Morbi wisi Cras dictumst quis diam Cum. Porta Nam Nunc fames nunc sed.",
                        "priority": "1",
                        "customfields": {
                            "f1": "Custom field ID 1 data",
                            "f2": "Custom field ID 2 data"
                        },
                        "attachments": {
                        "file": [
                            {
                                "ext": "jpg",
                                "data": "/9j/4SjeRXhpZgAA...}
                        ]
                    }

= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =

[17/November/2018 @ 19:49:47] Action/Info: Handler determined from incoming data: JSON

= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =

[17/November/2018 @ 19:49:47] Action/Info: [JSON] Reading data into readable array supported by all formats

= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =

[17/November/2018 @ 19:49:47] Action/Info: [JSON] Invalid API key

= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =

[17/November/2018 @ 19:49:47] Action/Info: [JSON] Nothing updated, check data or view log if enabled.

= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =

Any enlightenment will be appreciated.