Not too sure if there was something wrong with my run or not, but my run in which I have a faster time is obsolete but my older one is not. Does anyone know why this happened or what I can do.

It seems the leaderboard in question is sorted by IGT, but you filled in the RTA column and left IGT blank, so it's treating your newer run as slower. Given that most players aren't using the RTA column at all, the mods should probably just remove it.

Anyway, you'll need to take that up with the moderators of Monopoly Plus. Either ask them to fix your run or edit your run yourself to change the time to IGT, which will put it back in the mod queue.