Working on EU band but not US band

Hi,

I'm trying to set a LoRa network using a dragino shield with a raspberry pi 3 as a gateway and a MKR WAN 1300 as a node, in addition I'm using TTN (TheThingNetwork) to keep track of the data received at the gateway.

So far I've only had success with the EU band:
*TTN -> GW frequency plan: EU868MHz;
*Dragino -> running the single_chan_pkt_fwd with spreading factor = 7 and frequency: 868100000 (Find the code attached as main.cpp);
*MKR WAN 1300:

#include <MKRWAN.h>
#include "arduino_secrets.h"

// Select your region (AS923, AU915, EU868, KR920, IN865, US915, US915_HYBRID)
_lora_band region = EU868;

LoRaModem modem(Serial1);
//LoRaModem modem;

void setup() {
Serial.begin(115200);
while (!Serial);
if (!modem.begin(region)) {
Serial.println("Failed to start module");
while (1) {}
};
Serial.print("Your device EUI is: ");
Serial.println(modem.deviceEUI());

//int connected = modem.joinOTAA(appEui, appKey, devEui);
int connected = modem.joinOTAA(appEui, appKey);
//int connected = modem.joinABP(devAddr, nwkSKey, appSKey);
if (!connected) {
Serial.println("Something went wrong; are you indoor? Move near a window and retry");
while (1) {}
}
if(connected)Serial.println("Successfully joined the network!");

Serial.println("Enabling ADR and setting low spreading factor");
modem.setADR(true);
/*
DataRate Modulation SF BW bit/s
0 LoRa 12 125 250
1 LoRa 11 125 440
2 LoRa 10 125 980
3 LoRa 9 125 1'760
4 LoRa 8 125 3'125
5 LoRa 7 125 5'470
6 LoRa 7 250 11'000
*/
modem.dataRate(5);

}

void loop() {
modem.beginPacket();
modem.print("hi");
int err = modem.endPacket(false);

if (err > 0) {
Serial.println("Big success!");
} else {
Serial.println("Error");
}
delay(1000 * 60);
}

As I said this works, well at least I'm able to see at the GW join requests from the node (yes I've checked the devEUI and matches perfectly), I've attached an image directly from the TTN logs at the GW.

If I try to switch the frequency band, changing all the mentioned parameters (TTN, GW & Node) I have no success with the join requests meaning that I can't see any packet happening at the TTN or at the RPi console. I've tried changing the frequency value at the GW 902.3 - 914.9 changing the Spreading factor SF7-SF9. Without antennas ...

We have other nodes (dragino nodes) that are working at the US frequency band and I'm able to see the logs in the raspberry ssh console, therefore I believe that my GW is capable of supporting this frequency band and that I'm configuring it correctly.
Even if the Arduino MKR WAN 1300 is preconfigured at 868MHz, shouldn't be able to work at 915Mhz? we've got the ABX00017 (868MHz-915MHz).
I've also tried other Arduinos MKR WAN 1300 and I haven't had success....
Am I missing something in order to configure the US band? please help

main.cpp (17.9 KB)

I've tried another library that I found on github: sandeepmistry/arduino-LoRa after updating the SMT32 the arduino MKR WAN 1300 seems to work on the US band, only if using the sandeepmistry/arduino-LoRa library, but not the MKRWAN...

Any suggestion?