Greg,
Most 'auto-tuners' have limited tuning 'range' when
compared to 'manual' tuners, that's because of expense,
size limitations, and so on. Since I know nothing about
your 'LDG' tuner, that's what I'd have to guess is happening.
Doesn't mean that there's necessarily anything wrong with
it, just that it can't 'do' what you're asking of it...
'Doc