For HP exams, you need a “Learner ID.” Apparently your HP Passport account is not enough, and they like to maintain separate databases. Just to confuse things. You will need a Learner ID to get access to the HP Learning Center (where there is some free content), and to schedule exams.
It can take a few days to sort out access, and there are different processes for customers, partners and students. If you intend to pursue any HP certification, I highly recommend you get onto this part of the process early. You don’t want to be ready to schedule your exam, then get lost in the quagmire that is HP bureaucracy. So do it now! Go to “HP Learner ID | HP ExpertOne” and click the appropriate Customer/Partner/Student link.
Note that HP employees use their Employee ID for their Learner ID.