Giovanni, I forgot to ask: did you, the first time you tried with the newly downloaded ELAN 6.2, see the message window asking for permission to send events to Praat? And, if you go to System Preferences->Security & Privacy->Privacy tab and select the Automation category on the left, do you see on the right an entry for ELAN with a sub-entry for Praat (indicating that ELAN is allowed to send messages to Praat)?
-Han