VBA 400 Error when switching sheets

Here is my code below and I keep getting an error 400 message as soon as the code goes to the Priority Unique tab. It doesnt do anything on the tab except select it and then sends off the error. Thank you for the help.

Sub Email_Formats()
Dim wsTemplate As Worksheet: Set wsTemplate = Worksheets("Template (2)")
Dim iRowCount As Integer: iRowCount = wsTemplate.Range("H22").End(xlDown).Row
Dim a As Integer
Dim ws1 As Worksheet: Set ws1 = Worksheets("Macro Test")
Dim iRow1 As Integer, iRow2 As Integer, iRow3 As Integer, iRow4 As Integer, iRow5 As Integer
iRow1 = 250: iRow2 = 550: iRow3 = 950: iRow4 = 1250: iRow5 = 1500


For a = iRowCount To 2 Step -1
  If wsTemplate.Range("AG" & a).Value = 1 Then
      iRow1 = iRow1 + 1
      wsTemplate.Range("C" & a & ":S" & a).Copy ws1.Range("A" & iRow1)
      wsTemplate.Range("S" & a & ":S" & a).Copy ws1.Range("Q" & iRow1)
      wsTemplate.Rows(a).EntireRow.Delete
  ElseIf wsTemplate.Range("AG" & a).Value = 2 Then
      iRow2 = iRow2 + 1
      wsTemplate.Range("C" & a & ":S" & a).Copy ws1.Range("A" & iRow2)
      wsTemplate.Range("S" & a & ":S" & a).Copy ws1.Range("Q" & iRow2)
      wsTemplate.Rows(a).EntireRow.Delete
  ElseIf wsTemplate.Range("AG" & a).Value = 3 Then
      iRow3 = iRow3 + 1
      wsTemplate.Range("C" & a & ":S" & a).Copy ws1.Range("A" & iRow3)
      wsTemplate.Range("S" & a & ":S" & a).Copy ws1.Range("Q" & iRow3)
      wsTemplate.Rows(a).EntireRow.Delete
  ElseIf wsTemplate.Range("AG" & a).Value = 4 Then
      iRow4 = iRow4 + 1
      wsTemplate.Range("C" & a & ":S" & a).Copy ws1.Range("A" & iRow4)
      wsTemplate.Range("S" & a & ":S" & a).Copy ws1.Range("Q" & iRow4)
      wsTemplate.Rows(a).EntireRow.Delete
  ElseIf wsTemplate.Range("AG" & a).Value = 5 Then
      iRow5 = iRow5 + 1
      wsTemplate.Range("C" & a & ":S" & a).Copy ws1.Range("A" & iRow5)
      wsTemplate.Range("S" & a & ":S" & a).Copy ws1.Range("Q" & iRow5)
      wsTemplate.Rows(a).EntireRow.Delete
  End If
Next a
 
' Once our data is on the page it is time to start manipulating it to turn it into the right for for the emails
'

    Sheets("Priority Unique").Select
    Range("F251").Select
    Range(Selection, Selection.End(xlDown)).Select
    With Selection.Validation
        .Delete
        .Add Type:=xlValidateInputOnly, AlertStyle:=xlValidAlertStop, Operator _
        :=xlBetween
        .IgnoreBlank = True
        .InCellDropdown = True
        .InputTitle = ""
        .ErrorTitle = ""
        .InputMessage = ""
        .ErrorMessage = ""
        .ShowInput = True
        .ShowError = True
    End With
    Selection.Copy
    Range("A1").Select
    ActiveCell.FormulaR1C1 = "Name"
    Range("A2").Select
    Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
        :=False, Transpose:=False
    Application.CutCopyMode = False
    Range("A1").Select
    Range(Selection, Selection.End(xlDown)).Select.AdvancedFilter Action:=xlFilterInPlace, Unique:=True
    Range("A2").Select
    Range(Selection, Selection.End(xlDown)).Select
    Selection.Copy
    Sheets("Macro Test").Select
    Range("A2").Select
        Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
        :=False, Transpose:=False
        Selection.End(xlDown).Select
    Range("A80").Select
        Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
        :=False, Transpose:=False
    Range("A160").Select
        Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
        :=False, Transpose:=False
    Sheets("Priority Unique").Delete
    Sheets.Add().Name = "Priority Unique"
 
 Range("F551").Select
    Range(Selection, Selection.End(xlDown)).Select
    Selection.Copy
    Sheets("Sales Unique").Select
    Range("A2").Select
    Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
        :=False, Transpose:=False
    Range("A1").Select
    Application.CutCopyMode = False
    ActiveCell.FormulaR1C1 = "Name"
    Range("A1").Select
    Range(Selection, Selection.End(xlDown)).Select.AdvancedFilter Action:=xlFilterInPlace, Unique:=True
    Range("A2").Select
    Range(Selection, Selection.End(xlDown)).Select
    Selection.Copy
    Sheets("Macro Test").Select
    Range("A350").Select
        Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
        :=False, Transpose:=False
        Selection.End(xlDown).Select
    Range("A420").Select
        Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
        :=False, Transpose:=False
    Sheets("Sales Unique").Delete
    Sheets.Add().Name = "Sales Unique"
        
        
 Range("F951").Select
    Range(Selection, Selection.End(xlDown)).Select
    Selection.Copy
    Sheets("Deleted Unique").Select
    Range("A2").Select
    Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
        :=False, Transpose:=False
    Range("A1").Select
    Application.CutCopyMode = False
    ActiveCell.FormulaR1C1 = "Name"
    Range("A1").Select
    Range(Selection, Selection.End(xlDown)).Select.AdvancedFilter Action:=xlFilterInPlace, Unique:=True
    Range("A2").Select
    Range(Selection, Selection.End(xlDown)).Select
    Selection.Copy
    Sheets("Macro Test").Select
    Range("A750").Select
    Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
        :=False, Transpose:=False
    Selection.End(xlDown).Select
        Range("A820").Select
    Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
        :=False, Transpose:=False
    Sheets("Deleted Unique").Delete
    Sheets.Add().Name = "Deleted Unique"
        
    Application.DisplayAlerts = True
End Sub

I am taking data from the template (2) sheet to the Macro Test sheet. Once that data is copied in I am trying to generate a unique list of data for each section by copying the section over to another tab and running an advance filter on it for uniques only. My code is below and this is a very important project I am trying to do so any help would be greatly appreciated. I keep getting an error 400 message as soon as the code goes to the Priority Unique tab. It doesnt do anything on the tab except select it and then sends off the error. Thank you for the help.

Is that a sheet in the active workbook? If not, activate the workbook, and then select the sheet.

That said, it would be better if you removed all the Selecting from your code.