"What have you been doing?"
Translation:O que você tem feito?
You need to include the subject pronoun. Also, the pretérito perfeito composto is formed by "ter" + the particípio passado -> feito.
You can use a more colloquial form with "andar" and "vir" + gerúndio.
• O que você vem fazendo?
• O que você anda fazendo?- less formal
Source: Modern Brazilian Portuguese Grammar - Whitlam
I've had a similar problem. I see why it is better to include você, but it isn't wrong, is it? Also, I get a very strange explanation of my mistake, namely: "You used the ele/ela form "tem" instead of the você form "tens"." Even if "o que tem feito" won't be accepted, could the explanation at least be fixed?
Edit: I wanted to see what would happen and put in "O que você tens feito" and was told: "You used the você form "tens", instead of the ele/ela form "tem"." Please, fix the explanations...
This is an instance of the mind-bending, reality-distorting Portuguese Pretérito perfeito composto tense. It refers to a repetitive series of events extending from the past into the present, and is not really a "perfect" tense. It is sometimes replaced by the VIR (present) + Gerund construction.
For more glorious information, see Danmoller's excellent post on the subject:
Now, if i could only remember all this in the future, I'll be golden. :-)