I'm not familiar with the Mery rig. But as far as joint visibility is concerned, look for a connection to the root joint's visibility channel. Or if the root joint is parented, look up the hierarchy chain to find a visibility connection. If there is no connection, then look at the draw style of the joints themselves. Select a joint from the outliner and look in the Attribute Editor. The style might be set to "None". If so, then set it back to "Bone".
Also, are joints displayed in your viewport? Might there be a display layer for the joints? These are the various ways joint visibility might be affected.
