If playing multiplayer and you are NOT the host, when you try to enter an unlocked Sunken Crypt in the Swamp, sometimes, you may see the message: BLOCKED. There will be a stone wall as if the entrance is a dead end. Fully unequip your weapon. Even if it is sheathed (put away), it will still block you from entering. Your weapon must be unsheathed and inactive on your hot bar.