VEN have to send an oadrRequestEvent message for syncing with the VTN

[juantxorena]

As per the specs:

oadrRequestEvent - Used in a pull exchange model by the VEN to retrieve all
relevant events from the VTN. Used as the primary polling mechanism for A profile
VENs, but only used on B VENs for syncing with the VTN.
• oadrDistributeEvent - Used by the VTN to deliver demand response

I solved it temporarily by "await self.request_event()" before the client starts polling