Excel VBA Macro No Longer Works (Possible issue with http.Send) - vba

Question

I have a little Excel VBA macro that retrieves the stock value for a given company on a given day. The company is specified by passing in their stock symbol ("AZO" for AutoZone, "WMT" for Wal-Mart, etc.), and the date is an actual date value retrieved from an adjacent cell.
It has been working beautifully for 2.5 years, but this week it just stopped working, even though I didn't change anything whatsoever. Where the macro should be returning a value, now it's just returning #VALUE!. When I step through the code, everything is working fine until I get to the .Send(), where it just stops (no error messages or hints as to what went wrong; it just completely stops as if execution were finished). I tried adding an On Error clause but it doesn't get hit. Note: I'm thinking it doesn't make a difference, but originally I had http.Send with no parentheses, but I saw a lot of examples with ("") so I added that but it appears to not have an effect.
My VBA experience is very limited, so I was hoping someone would be able to point me in the right direction.
CODE:
Function StockQuote(strTicker As String, Optional dtDate As Variant)
' Date is optional - if omitted, use today. If value is not a date, throw error.
If IsMissing(dtDate) Then
dtDate = Date
Else
If Not (IsDate(dtDate)) Then
StockQuote = CVErr(xlErrNum)
End If
End If
Dim dtPrevDate As Date
Dim strURL As String, strCSV As String, strRows() As String, strColumns() As String
Dim dbClose As Double
dtPrevDate = dtDate - 7
' Compile the request URL with start date and end date
strURL = "http://ichart.finance.yahoo.com/table.csv?s=" & strTicker & _
"&a=" & Month(dtPrevDate) - 1 & _
"&b=" & Day(dtPrevDate) & _
"&c=" & Year(dtPrevDate) & _
"&d=" & Month(dtDate) - 1 & _
"&e=" & Day(dtDate) & _
"&f=" & Year(dtDate) & _
"&g=d&ignore=.csv"
Set http = CreateObject("MSXML2.XMLHTTP")
http.Open "GET", strURL, False
http.Send ("")
strCSV = http.responseText
' The most recent information is in row 2, just below the table headings.
' The price close is the 5th entry
strRows() = Split(strCSV, Chr(10)) ' split the CSV into rows
strColumns = Split(strRows(1), ",") ' split the relevant row into columns. 1 means 2nd row, starting at index 0
dbClose = strColumns(4) ' 4 means: 5th position, starting at index 0
StockQuote = dbClose
Set http = Nothing
End Function

Answer 1

Ran into this same issue today with VBA code that has been working fine for many years. Thanks to this post, not only was I able to get it working again by using https. But I may know the underlying cause as well.
Believe the underlying cause may be perhaps finance.yahoo.com has enabled HSTS. This would mean that once the site is visited using https. The use of https will be enforced for all future requests.
HTTP Strict Transport Security
https://en.wikipedia.org/wiki/HTTP_Strict_Transport_Security