@Victoria889 The amount you are eligible to be refunded depends upon the cancellation policy of the listing you booked. Each cancellation policy has different terms. When you book a listing you are entering into a contract to abide by those terms, so it's very important for guests to read and understand the host's policy before committing to a booking. Whether the length of time before the booking is "plenty of time", is irrelevant to the terms you agreed to. Some hosts will agree to a larger refund than their cancellation policy states if they are able to rebook those dates- you have to message the host and politely ask if they are willing to do that.
There is an extenuating circumstances policy both for guests and hosts that can allow you to cancel and receive a full refund, but the circumstances which that covers are quite specific. Simply being unable to make the trip isn't considered an extenuating circumstance.