Ah, yeah, I can reproduce that. Removing the first line (the #To get docs comment) fixes the issue. To use the help lookup, the ? character needs to be the very first thing in the cell.
You can get the same problem at the REPL:
julia> # This is a comment
?println
ERROR: UndefVarError: ? not defined
(note that I had to press alt-enter after the comment line to get a new line without executing anything)