OP again. Figured this out by looking at their Facebook page. Apparently if the family only has a free basic membership and the nanny has the same, the family can not see or reply to applications or messages from potential candidates.
I don't think it used to be this way. So basically the family or the nanny has to be a paid member in order to get in touch with each other. I'm pretty sure only the families used to have to pay, and it should still be that way.
Nannies are on there to look for jobs so obviously they don't have any extra money laying around!
I went ahead and bit the bullet and signed up, but I am very cautious and plan to cancel after my 3 months, and monitor my credit card.