Encantar is like gustar. The word order is switched around to make it easier to construct the sentences at first: We love this house = This house enchants/delights us.
This house is really the subject of this sentence, so the verb has to be 3rd person singular: encanta.
For more info and practice, see studyspanish.com (Grammar Unit Four).
Why do we get it wrong when we type what we hear? If i always have to listen to it slower to catch the correct wording, then maybe Duo should speak clearly and articulate the word(s) better from the start, or it should actually state type what is said and not what you hear. I find this messes me up more often than not, and some words need more to go on to get the right statements being uttered.