Given that you have two different ID#'s, it is not surprising that the endorsement page is not working. (ISC)² recorded the fact that you passed the test to the ID# recorded in your PersonVue account. You now need to login to the (ISC)² account that has that same ID# to complete step 2. Per your initial comments, you are logging into an account that with a different ID# that has not passed the exam, so you will never be able to compete endorsement.
As stated a few times now on this thread, the only way to solve this is to call member services, talk to a human, and have them merge the two (ISC)² accounts into one. As @AlecTrevelyan says, reaching a human does require persistence,but it is also the only way to get this solved.
Leaving a voicemail is not an effective strategy at call centers which have a chronic queue. The problem being that when the phone rings just as soon as they hang up on the prior call, they tend to prioritize answering the phone ahead of checking voice mail. When they finally do get to your message, if your number does not work or goes unanswered, they go onto the next voice mail and might never get around to trying you again. (ISC)² is not alone in this problem. It happens at all busy call centers.
This gets more difficult if you are asking them to call internationally -- mostly because you will need to tell them which country code and city code to use and if the city code is required... and the agent needs to understand the sometimes difficult intricacies of international dialing.
We could sit around this forum and discuss how Member Services could better organize (increase staffing, larger queue, chat function, etc.), but none of that is of immediate help to you. Solving your problem requires you actually talk to a human. And again, as @AlecTrevelyan says,that can take persistence.
