Excel 2010-2016 upgrade and code not working unless cell in active workbook is highlighted

I just upgraded from excel 2010 to 2016 and now I am getting a debug error when I start the macro at the line 'Workbooks("Live Trade Monitor - IB.xlsm").Worksheets("Live Trades").Select' only if my cursor is selecting a cell in a separate excel workbook that I have open. If my cursor is selecting a cell in the active workbook in which this macro runs then the code runs correctly. If someone can help me correct this error I would appreciate it. Thanks


The error that I am receiving is
Run time error '1004'
Select method of worksheet class failed

 

Option Explicit
Dim iCount As Integer, iNumber As Integer, rStart As Range

Sub CopyLiveTradeData()


        Dim UserInput As Integer
    UserInput = MsgBox(Title:="Confirm Continue", _
                       Prompt:="Are you sure you want to start the PnL recorder?", _
                       Buttons:=vbYesNo)
    If UserInput = vbNo Then Exit Sub
    
    'If user clicked yes, any code below this point will run
    'For example:
    

    Application.OnTime TimeValue(ThisWorkbook.Sheets("Live Trades").Range("X57").Value), "StartOnTime"
        


End Sub

Private Sub StartOnTime()


    iCount = 0
    iNumber = 20000
    Workbooks("Live Trade Monitor - IB.xlsm").Worksheets("Live Trades").Select
    
    
    Call OnTimeMacro
    


End Sub

Private Sub OnTimeMacro()



    If Time < TimeSerial(15, 59, 0) Then
        iCount = iCount + 1
        Application.OnTime Now + TimeValue("00:00:30"), "RunEveryXMinute"
    Else
        Workbooks("Live Trade Monitor - IB.xlsm").Worksheets("Live Trades").Select
    End If
    

    
End Sub