"Вони не слухають радіо."

Translation: They do not listen to the radio.

[average..joe]

The article here is unnecessary. Radio can be either the unit (and you'd use "the") or an uncountable noun like music, television, etc.

[Piece_o_Ham]

I personally would say "the radio". But I see what you mean; is it not accepted without it?

[Anna_Elsa_J.]

"They don't listen to radio" isn't accepted.

[sagitta145]

Thanks, fixed it

[JJe2s7]

"They did not listen to the radio" should be the correct answer.