Having the article before a possessive is much more common in Portugal and other Portuguese-speaking countries outside of Brazil.
But, there is an exception (there always is...) and that is with singular family members. Then it is okay to drop the possessive article (it goes back to a bible thing I have been told).
I believe Duolingo keeps changing the use of the article because it is opitional. You can say "o meu esposo" and "meu esposo" meaning the same thing. The difference is: when you add the article before the pronoun, you’re emphasizing the noun. It’s not exactly a rule, therefore :)
Why is "ele nao e o meu esposo" marked as incorrect? I thought that the 'o' was required when followed by a noun, in this case 'husband'...!
The article (here it is "o") in the possessive is optional in BR PT but not so much in EU PT.
At issue here is "e" without the acute accent is not optional in either PT as otherwise it means "and" rather than "is" (3rd Person singular "to be" from "ser"). He not and my spouse...
However, if the program is still not accepting the article (even with the correct verb) then it needs to be reported as it is proper Portuguese, even in Brazil.
Official word from one of the PT officials here: