You have the wrong call signature for the start_tla
callback in your VBA code.
If you open up your file in Custom UI Editor, there is a button called Generate Callbacks to the right in the menu. If you press it, it will give you the correct callbacks for your VBA code to match the ribbon xml in your file:
'Callback for buttonFormatTLA onAction
Sub start_tla(control As IRibbonControl)
'Your code goes here
End Sub
According to the Pastebin link, your sub looks like this, without the control As IRibbonControl
parameter:
Public Sub start_tla()