Why can’t I access a certain part in the game when other players can?

1. The thing that probably hinders you is a constellation gate (as shown in the image below). These are like barriers that refrain you from entering until you earn (or meet) the indicated number of spirits required to open them. You’ll see the number required in the barrier itself, and if you get all of what is asked, you will be able to unlock and access that area. Not limited to this, other constellation gates require more than just having to meet a number of ancestor spirits. Some do require items that are only found on other kingdoms -- promoting the need to revisit them later in the game.

2. The place that you are probably trying to access requires the participation of multiple players. Some rooms or areas in the game require people to play it in groups. These are usually the diamond-shaped items beside gates that are closed. There are some instances where you’ll see them opened when a previous group just seconds ahead of you recently accessed that part -- which will most likely show you that the gate is opened for them. However, if you try to get there, you still wouldn’t be able to trigger the event that should happen there. Nonetheless, this is why it is very important to gain a lot of friends in the game.