Update database via PUT http functions (json) with Excel/VBA

I've managed to interact with a database set up for testing purposes on Wix. I'm able to upload json data to it and I can see it in the LIVE database, albeit crudely. The issue is it just keeps inserting new rows/columns and I'm genuinely stump as to how I can get it to interact with existing fields.

Here's the Backend file code:

export function post_myFunction(request) {
let options = {
"headers": {
"Content-Type": "application/json"
}
};

// get the request body
return request.body.text()
.then( (body) => {

// insert the item in a collection
return wixData.insert("zpage_test", JSON.parse(body));

} )
.then( (results) => {
options.body = {
"inserted": results
};

return created(options);
} )

// something went wrong
.catch( (error) => {
options.body = {
"error": error
};

return serverError(options);
} );
}
Here's the VBA PUT code (..with Microsoft Scripting Runtime enabled in VBA references)

Sub SendJson()
Dim objHTTP As Object
Dim Json As String
Dim result As String
Set objHTTP = CreateObject("MSXML2.XMLHTTP")

Url = "https://www.mywebsite.com/_functions/myFunction"

Json = "{""ID"":""d0f6f64a-e6d8-4cac-9285-d3e51bf3cb53"",""Title"":""tTitle1"",""t1"": ""1.5"", ""t2"": ""hello""}"
objHTTP.Open "PUT", Url, False
objHTTP.setRequestHeader "Content-type", "application/json"
objHTTP.Send (Json)
result = objHTTP.responseText

'Some simple debugging
Range("A15").Value = result
Range("D15").Value = Json
Set objHTTP = Nothing
End Sub

could some insight be provided as to whats failing here? I'd really appreciate your help!

---UPDATE TO THE INQUIRY!---

I'm still trying to get it to work.. Here’s the updated code:

---WIX BACKEND---

import {created, serverError, ok, notFound} from 'wix-http-functions';
import wixData from 'wix-data';
export function put_myFunction(request) {
let options = {
"headers": {
"Content-Type": "application/json"
}
};

// get the request body
return request.body.text()
.then( (body) => {

// update the item in a collection
return wixData.update("zTest_DevDaily", JSON.parse(body));
} )
.then( (results) => {
options.body = {
"inserted": results
};
return ok(options);
} )

// something went wrong
.catch( (error) => {
options.body = {
"error": error
};
return serverError(options);
} );
}

export function post_myFunction(request) {
let options = {
"headers": {
"Content-Type": "application/json"
}
};

// get the request body
return request.body.text()
.then( (body) => {

// insert the item in a collection
return wixData.insert("zTest_DevDaily", JSON.parse(body));
} )
.then( (results) => {
options.body = {
"inserted": results
};
return created(options);
} )

// something went wrong
.catch( (error) => {
options.body = {
"error": error
};
return serverError(options);
} );
}

---EXCEL / VBA---

Sub SendJson()
Dim objHTTP As Object
Dim text As String
Dim jSON As Object
Dim result As String

Dim rng As Range, items As New Collection, myitem As New Dictionary, subitem As New Dictionary, i As Integer, cell As Variant

Set objHTTP = CreateObject("WinHTTP.WinHTTPrequest.5.1")

Set rng = Range("A2:A2")
'Set rng = Sheets(1).Range("A2").End(xlDown)) 'dynamic range
i = 0
For Each cell In rng
Debug.Print (cell.Value)
myitem("Title") = cell.Value
myitem("ID") = cell.Offset(0, 1).Value
myitem("Owner") = cell.Offset(0, 2).Value
myitem("Created Date") = cell.Offset(0, 3).Value
myitem("Updated Date") = cell.Offset(0, 4).Value
myitem("VerDate") = cell.Offset(0, 5).Value
items.Add myitem
Set myitem = Nothing
Set subitem = Nothing
i = i + 1
Next

URL = "https://www.MYWEBSITE.com/_functions/myFunction"
objHTTP.Open "PUT", URL, False
objHTTP.setRequestHeader "Content-type", "application/json"
objHTTP.Send ConvertToJson(items, Whitespace:=2)
result = objHTTP.ResponseText

'Some simple debugging
Range("A25").Value = result
Range("A26").Value = ConvertToJson(items, Whitespace:=2)
Set objHTTP = Nothing
End Sub
--

I'm using EXCEL/JSON convertor: https://github.com/VBA-tools/VBA-JSON

I've copied the database in excel to then apply the conversion and this is what a json entry value looks like:

[
{
"Title": "test1",
"ID": "a4ef53df-903c-44e5-a014-f8ae1d937b5f",
"Created Date": "2019-06-21T17:43:38Z",
"Updated Date": "2019-06-23T19:23:51Z",
"VerDate": 3
}
]

POST works
PUT generates the following error (invalid token???):
"{"error":"name":"Error","errorGroup":"User","code":"WD_VALIDATION_ERROR"}}"

That said, I'd really appreciate anybOdy helping me crack this code as my website fundamentally depends on this working in the longrun.