Using TeXForm for subscripted variables

I tried following the answer in TeXForm and Symobilze, however, I have trouble making it work. I loaded the Notation packages and symbolized all expressions with a subscript as in the example. I defined the same test function using Ctrl+_, I do obtain the same output for TeXForm and FullForm before loading updateSubscriptTraditionalForm[]. However, after loading it, TeXForm still gives me the same output?