VBA JSON POST Payload Issue - json

Question

I'm trying to setup a API request to pull data from the Bureau of Labor Statistics. I succeeded in getting data using a get request, entering just the url and the series (as shown in the first code example). This works fine and I was able to parse out the JSON using Tim Hall's VBA-JSON converter and work with the data. My problem is that the get method returns only 3 years of data and I'd like to get more than that which requires a post method.
Sub GetCPItable()
Dim objhttp As Object
Dim strUrl As String
strUrl = "https://api.bls.gov/publicAPI/v1/timeseries/data/CUUR0000SA0"
Set objhttp = CreateObject("MSXML2.XMLHTTP")
With objhttp
.Open "get", strUrl, False
.Send
End With
MsgBox objhttp.ResponseText
End Sub
It seems (take this with a grain of salt, this is my first time working with api servers) like VBA is not passing my payload. I've checked my payload here and the JSON syntax appears correct and seems to be the correct syntax according to the page I first linked to. Yet the only things I recieve back from the api server is 404 not found errors. I've been trying different things to piece together what I'm missing all day from their source code examples (no VBA ofcourse) and posts here and elsewhere on the web and haven't made any progress. Here is a debugging version of the code that isn't working.
Sub GetCPItable()
Dim objhttp As Object
Dim body As String
'create our URL string and pass the user entered information to it
Dim strUrl As String
strUrl = "https://api.bls.gov/publicAPI/v1/timeseries/data"
Set objhttp = CreateObject("MSXML2.XMLHTTP")
With objhttp
.Open "POST", strUrl, False
.SetRequestHeader "Content-type", "application/json"
body = "{""seriesid"":""CUUR0000SA0""],""startyear"":""2008"",""endyear"":""2012""}"
.Send (body)
End With
MsgBox objhttp.ResponseText
End Sub
This is the error I get in response:
: responseText : "{
"status": "REQUEST_FAILED",
"responseTime": 0,
"message": [
"404 Error - Page Not Found"
],
"Results": [ ]
}" : String
Any help would be much appreciated. The only thing I can think to try next is using the V2 API but I'd like to avoid that if possible since it would require yearly reregistration.