"SerializationError" when trying to write orders.

Trying to write orders from my website and getting this error in the Add on connector log file:

2019-07-25 16:52:41.7752 LogLevel=Info;CorrelationId=b26fbd0c-6732-4635-9029-79734905203b;DevKey=;CFileId=8409c60a-be74-4e01-aaf9-56e3501d591c;CodeArea=GateExit;ProductCode=0;ProductVersion=2019.2;HttpMethod=POST;Resource=/Sale/Order/Item;Query=;ResponseCode=400;StatusCode=BadRequest;HttpHeaders=x-myob-webapiexception=V1.0;x-myobapi-requestid=b26fbd0c-6732-4635-9029-79734905203b;x-myobapi-elapsed=743;ElapsedMilliseconds=743;ResponseData={
"Errors": [
{
"Name": "SerializationError",
"Message": null,
"AdditionalDetails": "Error converting value \"Product Sales\" to type 'System.Guid'. Path 'Category.UID', line 1, position 245.",
"ErrorCode": 50,
"Severity": "Error",
"LearnMore": null
}
],
"Information": "Warning, error messages have not been finalised in this release and may change"
}

We use AccountRight2019.2 with Categories turned on and required (new feature).  We were using Enterprisev19.15 and had this working ok under that.   The new version has us stumped as to how to specify the category correctly.

The category ID in myob is "Product Sales"

Any help appreciated.

Erynn