Using <DataTestMethod>, <DataRow....> with vb.net . Only one <DataRow> gets executed - vb.net

Question

I'm trying to set up an automated unit test using MSTest. I have single tests working, and am now trying to set up parameterised tests using < DataTestMethod> and < DataRow(...)>. I'm following the examples here
When I debug the test sequence below, the ParseTestData( ) is only called once, with the first <DataRow ..> parameter. It is not called a second time.
Can anyone see where I'm going wrong?
(Note: I found some articles indicating DataTestMethod is obsolete, and TestMethod works just the same. I tried and got identical results)
[edit] - from #Mark Seemann 's suggestion, I've simplified this from the original post. Same problem.
Imports Microsoft.VisualStudio.TestTools.UnitTesting
Namespace TestDecoder.Tests
<TestClass>
Public Class DecoderTests
Private DecoderInstance
<DataTestMethod>
<DataRow(New Byte() {&H41})>
<DataRow(New Byte() {&H42})>
Public Sub ParseTestData(Frame() As Byte)
Dim result As Boolean
DecoderInstance = New Decoder()
result = DecoderInstance.parse(Frame(0))
Assert.IsTrue(result, "Failed the dummy test")
End Sub
End Class
End Namespace
I'm not sure if this will provide any more insight, but here is the Decoder code (Edited for Brevity).
Imports Microsoft.VisualBasic
Public Class Decoder
Function parse(rxchar As Byte) As Boolean
Return rxchar = &H41
End Function
End Class