Der, die or das?
neuter noun · single-family house · level A2
die Einfamilienhäuser - in the plural, every German noun takes the article die.
"Einfamilienhaus" doesn't follow any of the 35 gender rules - it belongs to the words you learn together with their article, as one unit: das Einfamilienhaus. That's exactly what the app's spaced repetition is for.