Example LoRaWan OnBoardGPS_A530 and I2C-Module no right function

I take the example LoRaWan OnBoardGPS_A530 (HTCC AB 02s) and i want to read the temperature from the I2C-IC STS35 and put it in the LoRaWAN-Packet with the GPS-Data!

The testsequence in the normal arduino-loop worked fine and give me updated values.

Wire.begin();
Wire.beginTransmission(STS35_I2C_ADDRESS);
Wire.write(0x21); //
Wire.write(0x30); // send cmd
Wire.endTransmission(true);
delay(1000);
i=0;
Wire.requestFrom(STS35_I2C_ADDRESS, 3,true);
while (Wire.available()) { // slave may send less than requested
buf[i++]= Wire.read(); // receive a byte
}

When i test the sequence in the example in the function “prepareTxFrame( uint8_t port )”

it doesnt work! It seems the command will be send without an error, but i receive no data!

Any hints?

Greeting

E_T