Is it something called a "run time package"/RTP some older versions of RPG Maker need you to download it from the RPG Maker website. If you do need a run time package, this game would need XP. (Have no idea if this is your problem, because I got XP a while back and have the RTP.)
Viewing post in Milk Run (uncomplete demo) jam comments
I was able to play, hooray! Well, I liked the way the game is drawn. The characters look good. There is something attractive about them.
I have some remarks. I was a little confused at the beginning of the game. We wake up in bed and the game does not explain to us at least approximately who we are and why we are here. It may be worth considering how this can be changed. In addition, it is probably possible to somehow make the paverapes a more significant part of the game, it would be great.
It's great that you also wrote the walkthrough and posted it. It helped me in some places.