KeithM, I had same issue, no problem for Phantom but F550 upgrade did not appear. I disconnected and connected again to Naza, changed screens a few times in Assistant and finally upgrade window appeared. Still not able to arm the motors though.
i upgraded yesterday and now the motors won't start whichever way I try. Did notice that I calibrate the sticks in Naza assistant and then go off and try to start up, nothing, back to assistant and the sticks are out of calibration or off center again. Re-calibrate and center again, try to start...