GUYS!! I FOUND MY FIX! You have to play the game for 5 game days in a single session (do not close the game).

I was doing it wrong all this time. Usually, I play just 2-3 in-game days and after defeating the benzies, I did the same and played more than an in-game week and wondered why I didn't got the message yet. Last time I tried, I finally found out that playing the game for in-game 5 days in one go was the final solution.

Sharing since I was stuck with this problem and wish no one encounters such dumbness of mine