In order to transmit radio data between board versions, eg sending and receiving between a micro:bit V1 and V2, you will first need set the radio group.

If you do not set the radio group, the micro:bit program assigns a group at random between 1-256 and due to the way the hex file is compiled, the random group can be different for a V1 and a V2.

Here is a table of current radio behaviour:

V1 - V1works
V1 - V2does not work without first setting the group
V2 - V2works

This GitHub issue provides more context

Set the radio group in MakeCode

From the radio toolbox menu, drag a radio set group block under on start

More information about how radio groups work in MakeCode

Set the radio group in Python 

Import the radio module and set the group as follows

import radio

More information about radio configuration in MicroPython