The duolingo definition for 'lararium' includes 'shrine'; but when I typed 'I do not live in a shrine', this was counted incorrect. Is there a reason I may not be considering for not using 'a shrine'?
One reason might be, that a lararium is a "household shrine" and not any shrine (as far as I can tell) - so maybe that's the reason. Other than that (if you didn't make any accidental typo) I don't see a reason why it shouldn't be accepted - try reporting it next time.
I typed "household shrine" as the hint suggests and it was accepted. As Sigurd notes, it is not just any shrine. It is a very specific thing.