HCM Adapter as a trigger , can't receive business event

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Hello all,
I'm using HCM Adapter as trigger , and choosed the business object to be (Business Unit).
Then i've saved and enabled the integration .
But when i open HCM and create a business unit to test my integration , nothing flows to OIC .. is there any confiugration needed to enable business events , or HCM is not mean to be used that way .. please advise
Thanks
Osama