"We had not heard you."

Translation: Δεν σε είχαμε ακούσει.

[jeanprendiville]

Why not " σας" plural?

[jaye16]

Yes, of course. Was σας rejected as "incorrect"? Please let us know because I see it clearly as an accepted translation. If it was rejected we'll have to look inot it. Thanks.

[jeanprendiville]

In Past Perfect Test Out. I do like the Test Outs, not because they give you quicker results but they are more demanding. I like the three strikes and your out, it encourages attention! It's good that they are an option because I know when they had it without choice in French, it discouraged some people. Judging from the remarks it even drive others crazy.

[Lng52-._]

If I wanted to add "εμείς", would it be: "Δεν σας/σε εμείς είχαμε ακούσει"?

[troll1995]

No, it would be "Εμείς δεν σας/σε είχαμε ακούσει."

[kathy140555]

apart from getting the accents on the 'e's rather than the 'i' s which usually doesn't matter for the score, I had the above which was marked wrong. Have you added σας ?

[jaye16]

Yes, "σας" is equallly correct. And while the accents are important you're right that Duo does not reject a sentence with missing or incorrect accents.
There might have been another issue. If you had a screenshot it would help us get to the root of this.