No, that should work, let’s have a look the LoRaWAN protocol document:
Refer to my picture, the LoRaWAN protocol set the AU915 upstream channel frequency:
Total 64 channels, 915.2MHz begin, incrementing linearly by 200KHz, and 927.8MHz end.
Then look back to our code:
in the channelsMaskTemp, 0x00FF means use the first 0~7 channels, they are 915.2MHz, 915.4MHz, 915.6MHz … 916.6MHz. When you set the value to 0xFF00, it means the upload channels changed to 8~15, they are 916.8MHz, 917.0MHz … 918.2MHz.
Now, I think you need to confirm your gateway’s listening channels and listening frequency. Make sure they match the 8~15 channels.