Because noi luăm masa means to eat meal, but noi măncâm masa means to eat a table. It's kinda like a phrase.
It accepted "We take the table" too - and now I am confused because "We eat the meal" means something totally different. I know that "masă" means "table" and "meal" but ... I don't know, I am just confused. Any enlightment available? :)
If you translate that sentence literally, then you get "We take the table".
But there's also a fixed expression in Romanian, "a lua masa" which basically means something like "to eat" or "to have a meal". It's the context, that provides the actual meaning. Without any context here, Duolingo accepts both translations.
”We take the table” and ”We eat the meal” are both correct, but with completely different meanings.