XBEE3 transparent mode with meshkit

I’m trying to use the modules in transparent mode Half duplex at 4800bauds.
With XCTU I’ve configured the DH and the DL of two boards.
When the dev “slave” board is plug to the USB the RX led blink and when I remove the USB and use a battery the RX led is still off.
Is there something to configure to tell the module to be in transparent mode all the time ?