Can't add loop cut with Ctrl+R When I try to add a loop cut by pressing CtrlR only a dot shows on my object instead of whole loop cut line. What am I doing wrong to cause this problem?
That happens if you are using the Loop Cut on an edge that isn't connected to the rest of the mesh.


Try selecting that lower edge and moving it down a little. If it is not connected then just delete it. If the edge you select is connected but you see that there was another edge hiding below it then select that edge and move/delete it.

Or you could select everything and from the Tools panel on the left and use the Remove Doubles tool.