Macro to Upload data to a different workbook is broken

I'm trying to write a Macro to upload data from one workbook called "OutcomeUpload" to the next empty row in "sheet1" on another workbook called "Postings". The code i'm using (below) finds and opens the "Postings" workbook but doesn't upload the data. I've tested the vba by posting to another sheet in the "OutcomeUpload" workbook instead of the "Posting" workbook and that works fine. However when I try to upload to the "postings" workbook I get an error message saying "Run Time Error" "Object doesn't support this property or method".

Sub OutcomeUpload() 
     
    Set wsForm = Sheet1 
    Set wsData = Workbooks.Open("C:\Excel\Postings.xlsm") 
    Worksheets("sheet1").Select 
     
    Set rNextCl = wsData.Cells(65536, 1).End(xlUp).Offset(1, 0) 
     
    With rNextCl 
        .Value = wsForm.Cells(20, 4).Value 
        .Offset(0, 1).Value = wsForm.Cells(20, 9).Value 
        .Offset(0, 2).Value = wsForm.Cells(20, 13).Value 
        .Offset(0, 3).Value = wsForm.Cells(20, 18).Value 
        .Offset(0, 4).Value = wsForm.Cells(20, 21).Value 
        .Offset(0, 5).Value = wsForm.Cells(20, 28).Value 
    End With 
     
    MsgBox "Upload Completed" & vbCrLf & "", vbInformation, "HELP" 
     
    wsForm.Range("OutcomeUpload").ClearContents 
     
    Set wsData = Nothing 
    Set wsForm = Nothing 
    Set rNextCl = Nothing 
End Sub

the following rows seem to be the problem I think

Worksheets("sheet1").Select 
     
    Set rNextCl = wsData.Cells(65536, 1).End(xlUp).Offset(1, 0)

Hope you can help