I was having trouble with a QUAD i upgraded ESCs and Motors on, I figured i would erase all the old settings and start fresh. In the CLI, I hit Reset, rebooted, then erase, everything worked properly. I rebooted once more, opened the latest version of Mission Planner went to install firmware, hit Quadcopter, it stops on Detecting Board, Did i miss a step some where?
Can you still talk to the APM with the CLI?
I believe that "erase" does not erase the existing firmware so something else is going on.
Did you try and communicate with the APM using the MP without trying to do an upload?
I suggest, if you can still communicate using the CLI, that you do a reset following the instructions and then an erase and see if you can still communicate using the CLI. If so, then disconnect and go back to the MP initialization page and try loading again.