Someone who continues to deliberately misgender after being told about it - especially using "he" when the person's name (Maia) is traditionally a woman's name - seems to care quite a bit.
If they truly don't care to perceive a gender then a 50 / 50 pick. When I look at it's picture I honestly couldn't tell you if I perceive more male or female so I would've done same as op and picked one randomly and then for consistency not change it, even if some unrelated party tried to confuse things by making me change it.