Exit all subs

Be careful of the use of End. It will reset all module/project level variables.

The problem is that the response variable is local to the caller routine.
You either need to use a public variable or a private variable within the userform that you can read.

public variable approach.

Public response As Integer
Private Sub CommandButton1_Click()
    
    Dim click As Integer

    click = ActiveSheet.Range("Z1")
    
    click = click + 1

    ActiveSheet.Range("Z1") = click
    
    UserForm1.Show
    
    If response = 1 Then
        Exit Sub
    End If
        
    Call NotifyDepartments(click)

End Sub