English Translation
What made it difficult for you to carry out the plan?
Robotic word-for-word translation… なにでしたか is especially unnatural. My alternative translations are:
どうしてあなたの計画はなかなか進まないのですか？= (lit.) Why doesn’t your plan make progress as much as you expected?
あなたの計画を阻むものは何ですか？（あなたのけいかくをはばむものはなんですか？）= (lit.) What hinders your plan?
Although the English sentence is written in a past tense, I think a present tense sounds better in Japanese because I interpret the meaning as “you still have the problem”.