How do I address an end device?

I’m trying to make a TX request to an end device using two XBee 868 devices. When I use 64 bit addressing the TX status byte is ‘0x75 - Indirect message unrequested’. But I can’t figure out how to use 16 bit addressing because the 16 bit (MY) address of the end device seems to be 0xfffe.

I’m sending from the coordinator.

What is your API frame and have you use the API frame maker to check to see if it is valid?

For the record, the solution to this problem was to re-configure the radio that I had set as a coordinator as a normal node (end device if I remember right). So the network has no coordinator, but this is OK with 868 radios apparently.