I'm using webforms and VB. I am calling Stripe to perform an ACH transaction. I have a standalone program that works, however when I put the code in my production application, the flow is not what I'm expecting.

I'm reading a gridview which contains customer IDs of records which need to be billed via Stripe. I have a button (btnPost) which starts the process. That button calls an Async Sub which loops through the gridview. For each row I call a "Post_ACHAsync" subroutine, which is also Async. Within the "Post_ACHAsync" subroutine is the call to Stripe, with an "Await", which returns a Task.

The problem is that, when the call to Stripe is done, it goes back to the For/Each loop instead of proceeding with code. Why is it doing that?

Here's the code:

Protected Sub btnPost_Click(sender As Object, e As EventArgs) Handles btnPost.Click

    PostTransactions()
    PopulatePendingTrxs()

End Sub


    Protected Async Sub PostTransactions()
        For Each row As GridViewRow In gvTrxs.Rows
            Select Case row.Cells(2).Text.ToUpper()
                Case "B"
                    '--- Bank Account (ACH)
                    Post_ACHAsync([parameters])
                Case "C"
                    '--- Credit Card
                    Post_CC(row)
                Case Else

            End Select
        Next
    End Sub


  Private Async Sub Post_ACHAsync([parameters])          
    dim oM as new BillingMaster()
    
      '--- call Stripe
          Try
              Dim stripeService As New StripeService()
              Dim chargeId As String = Await stripeService.ProcessAchTransferAsync([parameters])
              ' Success!
              oM.Status = "W"     'Withdrawal
              oM.SuccessOrFailure = "S"
              oM.StripeWithdrawalID = chargeId
              oM.StripeWithdrawalMsg = "Success"
              colErrors = oM.SaveRecord(oM)
          Catch ex As Exception
              OKtoContinue = False
              colErrors.Add(ex.Message)
          End Try

      If Not OKtoContinue Then
          oM.PostGUID = strPostGUID
          oM.Status = "F"
          oM.SuccessOrFailure = "F"
          oM.StripeWithdrawalID = ""
          oM.WithdrawalDate = DateTime.Now
          oM.StripeWithdrawalMsg = SplitErrors(colErrors)
          colErrors = oM.SaveRecord(oM)
      End If

      oM = Nothing

  End Sub   
  
  
  Public Async Function ProcessAchTransferAsync([parameters]) As Task(Of String)
    Try
        
        '--- do Stripe stuff here

        Return charge.Id
        
    Catch ex As StripeException
        ' Log the error
        System.Diagnostics.Debug.WriteLine($"Stripe Error: {If(ex.StripeError?.Message, ex.Message)}")
        Throw New Exception($"Payment processing error: {If(ex.StripeError?.Message, ex.Message)}")
        
    Catch ex As Exception
        ' Log the error
        System.Diagnostics.Debug.WriteLine($"General Error: {ex.Message}")
        Throw New Exception("An unexpected error occurred while processing your payment. Please try again.")
        
    End Try
    
End Function

After the Await stripeService.ProcessAchTransferAsync line, the flow goes back to the For/Each loop; it doesn't continue with the "Success" (or Catch) code.

Do I need both subroutines to be Async? Should there be another "Await" somewhere?