Just because the ticket is upgrade eligible does not mean that there is upgrade inventory, which is often quite limited for mileage upgrades.
Normally KLM should allow Y-J upgrades, if there is upgrade inventory, on YBM fares. Air France also allows upgrades, if there is inventory, on YBM fares but only one class of service, ie Y-W, W-J, not Y-J.
It's not entirely clear what exactly you've booked and how. For us to help you more you should specify your flight numbers in your itinerary it sounds like you booked through Delta?