I know this has been covered a few times, I read all the related post and still could not solve my issue. When trying to initiate a conference call, I dial the first number press the conference button dial the other number. while having both parties on the phone I am unable to join the calls. I get the two options to release me and trade calls but pressing the conference hard button button does nothing. I have a 5330. On a side note I have sip trunks and yes I did check the cos and yes I did check the maximum co trunks conference, as specified in the other related post. Please help.