I haven't seen you for several days now. Is everything alright with you?
I haven't seen you lately. Are things ok with you?
ーI haven't seen you for several days now. Is everything alright with you?
「何日か見かけなかったけど、大丈夫でしたか？」
ある過去の時点から現在に至るまで見かけなかったわけなので、現在完了形を使って言えます。
I haven't seen you for several days now.「ここ何日かあなたを見かけませんでした。」
ーI haven't seen you lately. Are things ok with you?
「最近見かけなかったけど、大丈夫？」
I haven't seen you lately. で「最近あなたを見かけませんでした。」
ご参考まで！
カナダ 
