In sample_app.c
SINK_ENDPOINT_ID and SRCE_ENDPOINT_ID should have the same value.
The ZB_APP_REGISTER_REQUEST message takes AppEndPoint as a parameter.
The API states that this value should be the same for all devices in the network.
These two values being different were preventing my Coordinator from being able to talk to an EndDevice.
Note: For those trying to send from Coordinator to EndDevice, I modified the
sinkEP and srceEP arrays to register commandId=1 as both an input and an output for both sinks and sources.
The function zb_SapiAppRegister must also be updated to handle the new length.