An error was reported from EA Online

Hello SylviaSliverTime​,

This could be an issue related to the specific server, also try joining servers from inside of Battlefield 4 (don't use Battlelog).

I just tried joining the server again through the client, but the same error message appeared. I suspected that I might have been banned from the server, but after checking with the server administrators, they confirmed there are no ban records associated with my account,and I can join other severs.This situation is truly puzzling.

If you are able to join other servers, then it's definitely something related to the one specific server you are trying to join.