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 - V1||works|
|V1 - V2||does not work without first setting the group|
|V2 - V2||works|
This GitHub issue provides more context https://github.com/microsoft/pxt-microbit/issues/3421
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 radio.config(group=1)
More information about radio configuration in MicroPython