Attended transfer whith manager APi

I try to use PlayDtmfAction.

the java code is:

 connexion = ConnexionAsterisk.getInstance();
 PlayDtmfAction pa = new PlayDtmfAction();
 mr = connexion.getManagerConnection().sendAction(pa, 20000);

the response is:
org.asteriskjava.manager.response.ManagerResponse: actionId=‘null’; message=‘DTMF successfully queued’; response=‘Success’; uniqueId=‘null’; systemHashcode=629020

The message on the manager is:

Feb 14 12:12:06 WARNING[7427]: channel.c:1604 ast_waitfor_nandfds: Thread -1223816272 Blocking ‘SIP/904-081b9688’, already blocked by thread -1224082512 in procedure ast_waitfor_nandfds

I don’t understand why the DTMF sequence is not send to the channel

Have you got a solution ?

Thanks for help !!