the CPDLC in inibuilds a340 not responding on aircraft's panel, I tryed a solution that works for me and is as follow:
1) ADIRS has to be aligned
2)verify in EFB that CPDLC is set to BYATC
3) compile and send departure clearance request and wait till BYATC app respond with clearance via text ON THE APP ,not the aircraft panel where it doesn't works at the moment
4) change in EFB CPDLC to HOPPIE
5) compile again the departure clearance request exactly as before and send again
6)in EFB reset CPDLC to BYATC 
7) WAIT and you will receive the reply correctly in Aircraft system

IMPORTANT ADIRS must be aligned before trying this procedure

reported also to BYATC team hope that someone could help solving this bug. thank you

Hi. We're investigating this and hope to have a solution soon. Thanks for the report. 

Same problem here, using BeyondATC or hoppie does not work, I am able to send the depart clearance request but never obtained a response message, neither in the APP nor in the aircraft. 

Any idea why this is happening??

Same here .  no connection with A340.   nothing on app or aircraft DCDU.   Strangely warning on MCDU says COMPANY MESSAGE RECEIVED  but no mesage received in RCVD MSGS list.   

Hoppie works for WX request but not BeyondATC.    meanwhile A350 works with clearance and WX with BATC