Ａ「お宅のこうちゃん、薬飲まないの？」
Ｂ「そうなの。あの子、（ ）、いやがって口を開けないのよ。」
１ 飲むことにしても ２ 飲むつもりでも
３ 飲ませたつもりでも ４ 飲ませようとしても
I chose ３ 飲ませたつもりでも. The correct answer is ４ 飲ませようとしても. I think
Ｂ「そうなの。あの子、（飲ませたつもりでも）、いやがって口を開けないのよ。」
means "I planned to make him drink it, but he hates it, and I can't open his mouth.", while
Ｂ「そうなの。あの子、（飲ませようとしても）、いやがって口を開けないのよ。」
means "I try to make him drink it, but he hates it, and I can't open his mouth." In English, these both sound fine to me, so I don't understand why ３ 飲ませたつもりでも is wrong.
I realized maybe the reason is Ａ is using the present tense, 薬飲まないの？, so using the past tense, 飲ませたつもりでも, is wrong. Is that why?