It might be that AutoIt can't actually get the text. Are you sure you're using the right object ID? You might have to try other Windows GUI tools instead. Something like these
For debugging the AutoItLibrary issue, I would first try and see if I could get it to work natively in AutoIt, which I'm guessing likely not (e.g. AutoItScript or via COM in python, vbscript. If using COM and python, you could interactively test/debug using the python shell to call the AutoIt APIs).