They should definitely be accepted, but the correct conjugation is estaréis

Spanish from Spain has become a strange and isolated variety of Spanish with it's own words and a remarkable different pronunciation of "s" "z" "ce" "ci" and "j". Nobody says vosotros here in America. Only less than 10% of native Spanish speakers use the peninsular variety. My cellphone's Latin American predictive dictionary doesn't even heve vosotros and It's conjugations, i'd have to shift it to the Spain variety just to write them.

Furthermore, haven't you noticed that the audios of this course are all in American Standard Spanish? They're trying to teach a standard Spanish here, what we call neutral. Peninsular Spanish is everything but neutral. It is the same in the portuguese course, they teach Brazilian and not Portugal's, and in English they teach American and not British. Decisions have to be made and neutral American Spanish was chosen. I'm from Argentina and in Rioplatense Spanish we use vos instead of tú, but it would be rather confusing for foreigner students to learn all and every variety. So for this course I stick to tú and ustedes, discarding vos and vosotros. I support this course being in the neutral American Spanish standard... Lo siento por vosotros! Vos sabrás entender!

CHRISTINE_MAY is right. I would report it.