As of yesterday, the process of consolidating multiple TBC Classic realms began, making those realms no longer available. This was announced in June and all the details can be found below :
Any characters that were still on one of these realms when they were taken down, will be automatically moved to a new realm, as outlined in the above post. They are not deleted or lost, but the process of moving the characters will take time and may be unavailable for up to two weeks.