Why does it show that the network is not connected?

[0x3fffff]

But this website shows that the server is running normally, and I can also find it in the game’s community servers.

The server has 2 CPU cores, 4 GB of RAM, and a 5 Mbps connection.All security groups on the server have been opened
Sometimes I can enter the game, but other times the connection fails. Sometimes two people can get in but can't see each other.