Hi - I too have this same issue. I can only see my Orders when I select History>Activity.
My orders are listed, but I can't interact with them (i.e. can't cancel/change, etc).
Along the top of the screen is an option: Working Orders. Selecting this doesn't bring up a window, in the same way it does if I select the other window top buttons such as Finder, Prices, Watchlist, etc.
Any other suggestions? Thanks.