So after purchasing the game, i wanted to join the discord channel by the link on main page https://discord.com/invite/CBJ9wbruAj
However, i quickly realize the showing steps is trying to create a new account for me to join discord.
I cancel it and login my discord application, and click the URL again.
However, this time the invitation windows show that "Can not accept the invitation"
Not even if i modify the settings for join an adult channel.
Is there anyway i can fix that?

Alright. After some research, I still can’t join the channel. However, I noticed that I can always create a new account to join. Therefore, I guess this is somehow related to the age verification. My account was created very early, so I don’t remember verifying it before. 

I solved this problem by:

In the family center option of Discord, I get to verify my age again. After that, I joined the channel with no other issues.

Yeah Discord has classed it as a nsfw server, so some people have trouble joining it because Discord doesnt let them :(