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Product Registration is required to associate the PBX Appliance product and Support Contract with your Support Portal account. Each PBX that has a support contract has an associated Deployment ID and you open the ticket based on the Deployment ID. If the Deployment you are trying to open a support ticket for is not shown in your portal account you will need to make a product claim to have it show up as outlined here How to Co-Own a product that is not linked to your account