If there is a particular IPO that you would like to participate in that is not visible to you by clicking on the Trade menu followed by IPO Subscription in Client Portal, its listing details may not be publicly available yet. If the IPO details are publicly available but you cannot see the IPO in Client Portal, IBHK may not be supporting applications for the IPO, or you may not be eligible to participate.
Please contact IBKR Client Services to assist you if you cannot find an IPO you would like to participate in.