You're only missing two brackets/parentheses!
When you use a reactive expression elsewhere (e.g. in your renderPrint() call) you need to use () after the reactive name.
So you can change your renderPrint() to:
output$display <- renderPrint({
as.character(tpl_info_A()[["TPL_EmissionsLimit"]])
})
(I removed the return() call, too, as you don't need it).
For a good start to understanding reactivity, I'd recommend checking out the videos from the Shiny developer conference.