That will be "We didn't solve it."

Personally, I might have said solution as 解决办法, as 办法 equates more to "way/method" in my mind, but Duo is correct here, and 没有办法 is an oft used expression for not being able to do something about a situation.

The option with 解决 is wrong because that sentence ends with 不客气 instead of 对不起.