I think that correct Portuguese should have an article "a" before "minha":
"Eu não consigo encontrar a minha chave"
Both are correct. I hope this may help you: http://duolingo.com/#/comment/64947 ;)
Fair enough. In that case then, the sentence with the article should also be accepted as correct.
Yes ;)
"I can not find my keys" and "I cannot find my keys" should be marked as the same answer.
What's the difference between posso and consigo?
Posso = I'm allowed to
Consigo = I'm able to