Reset range selection

Question

I track our writers' monthly payments, and have created a workbook with a worksheet including a summary of each writer's pay.

The sheet includes a vlookup that returns each writer's email address, a subject and introduction line, and the summary.

I have VBA code that selects the range with the summary, fills out the To:, Subject:, and Intro Fields, and emails the selection at the click of a button.
I need to do this multiple (about a dozen) times, one for each writer, each month.
The code works the first time, but in subsequent runs, instead of placing the range in the email body, it places the entire sheet.

How do I "reset" so I can email a summary, change to a new writer, and run the macro again "fresh," once for each writer, each month?

The code, found on the internet, amended by me. I tried to reset the SndRng selection to Nothing, but that did not work:

Sub Email_Earnings_Summary()
'Working in Excel 2002-2016
Dim AWorksheet As Worksheet
Dim Sendrng As Range
Dim rng As Range
Dim tomail As String
Dim subjmail As String
Dim intromail As String

tomail = ThisWorkbook.Sheets("Payment Email").Range("e10").Value
subjmail = ThisWorkbook.Sheets("Payment Email").Range("e11").Value
intromail = ThisWorkbook.Sheets("Payment Email").Range("e12").Value

On Error GoTo StopMacro

With Application
    .ScreenUpdating = False
    .EnableEvents = False
End With

'Fill in the Worksheet/range you want to mail
'Note: if you use one cell it will send the whole worksheet
Set Sendrng = Worksheets("Payment Email").Range("c15:g33")

'Remember the activesheet
Set AWorksheet = ActiveSheet

With Sendrng

    ' Select the worksheet with the range you want to send
    .Parent.Select

    'Remember the ActiveCell on that worksheet
    Set rng = ActiveCell

    'Select the range you want to mail
    .Select

    ' Create the mail and send it
    ActiveWorkbook.EnvelopeVisible = True
    With .Parent.MailEnvelope

        ' Set the optional introduction field thats adds
        ' some header text to the email body.
        
        .Introduction = intromail

        With .Item
            .To = tomail
            .Subject = subjmail
            .Display
        End With

    End With

    'select the original ActiveCell
    rng.Select

End With

'Activate the sheet that was active before you run the macro
AWorksheet.Select

StopMacro:
    With Application
        .ScreenUpdating = True
        .EnableEvents = True
    End With
    'ActiveWorkbook.EnvelopeVisible = False
    Set SndRng = Nothing
End Sub

Note: I also tried changing the line

'Activate the sheet that was active before you run the macro
AWorksheet.Select

to SndRng.Select. After one run, I get a message that the message was already sent, and the button to "Send this Selection" changes to "Send this Sheet."