How to set string in the structure part of NRF24?
Did you actually 'instantiate' the struct in the TX and construct sensor1 as payload.sensor1 = ...? Anyways, there's still a problem.

You are using String in your payload. The third argument to read is the maximum message length that can be stored in payload. In your read call, you passed the size of payload as MAX_LEN. You will receive incomplete payloads since the String object in the RX payload struct has no content in it yet and thus payload's size, which you passed as MAX_LEN, will be less than that of the actual payload that was transmitted. Just ditch the Strings and try:

TX:

int vals = {x, y, z};   // guessing they are ints

network.write(header, &amp;vals, sizeof(vals));


RX:

int vals[3];
network.read(header, &amp;vals, sizeof(vals));

Serial.print(vals[0]); Serial.print(',');
Serial.print(vals[1]); Serial.print(',');
Serial.println(vals[2]);