I have a similar problem to the OP. I am trying to place a mechanical symbol (mounting holes, which I have done before on this board and others) on a board where I have already placed and routedmy components.
Unfortunately, when I do Place-> Manual... like I did before, I get the same message in the command "Select elements to place using tree view.", but I can't see it!
I know the tree view its referring to, but I don't seem to be able to get that view to come up again, no matter what I do. Any suggestions?