DownLink Failed

Based on the information provided, it appears that you're experiencing issues with downlink messages failing and the LNS (LoRaWAN Network Server) selecting SF12 (Spreading Factor 12) for long downlink messages, despite having configured DR (Data Rate) settings in your service profile.

The problem likely stems from a mismatch between your device profile and service profile configurations. In your device profile, you've set RxDataRate2 to 10, which is appropriate for the US915 region. However, in your service profile, you've set DrMin to 9 and DrMax to 13.

For the US915 region, the valid data rates typically range from 0 to 4 (for 125 kHz channels) and 8 to 13 (for 500 kHz channels). Your DrMin and DrMax settings in the service profile are only covering the 500 kHz channels, which may be causing issues with downlink communication.

To resolve this, try adjusting your service profile settings:

1. Set DrMin to 0 (or the lowest data rate you want to allow)
2. Keep DrMax at 13 (or the highest data rate you want to allow)

This change will allow the network server to use a wider range of data rates, including slower ones that might be necessary for longer downlink messages or challenging radio conditions.

Also, ensure that your gateway is properly configured to support all the channels and data rates you intend to use. The FactoryPresetFreqsList in your device profile looks correct for US915, but verify that your gateway is set up to listen on these frequencies.

If you continue to experience issues after making these changes, you may need to investigate further by:

1. Checking the signal quality and RSSI (Received Signal Strength Indicator) of your devices
2. Verifying that there are no environmental factors interfering with signal propagation
3. Ensuring that your devices are within range of the gateways

Remember that LoRaWAN is designed to adapt to different conditions, and sometimes slower data rates (like SF12) are necessary to ensure reliable communication over longer distances or in challenging environments.
Sources
LoRaWANGetServiceProfileInfo - AWS IoT Wireless
LoRaWANMulticastSession - AWS IoT Wireless
LoRaWANDeviceProfile - AWS IoT Wireless