SkyStatus request failed (No parameterless constructor defined for type of 'System.String'.)

We have been using the API https://unityapi.webrootcloudav.com/service/api/status/site/{GSMKey} for many months now and it has been working fine until this morning.

I have started receiving the following response and was wondering why this woudl suddenly be the case. I am getting the same result from other API calls for the endpoint status.

{

    "statusCode": 500,

    "requestId": ",

    "error": null,

    "error_description": "SkyStatus request failed (No parameterless constructor defined for type of 'System.String'.)",

    "AdditionalInformation": {}

}