"A magas énekesnők nem fiatalok."
Translation:The tall singers are not young.
The tall women singers are not young, it translated énekesnők to just singers instead of women singers.
It's more frequent to make this distinction (énekes vs. énekesnő) in Hungarian than in English. I've seen "female singer" and even "woman singer" (is that correct though?) in English texts, but only when it was absolutely necessary to express or emphasise the gender.
The translation accepted as being correct is inconsistent . While in English, the gender-specific phrase "female [or] women singers" is perhaps less common, it doesn't mean that "énekesnők" (literally "female singers" and as indicated by DuoLingo) - should not be accepted as an alternate translation.