The .heliohost.org domains are no longer available to regular users (they were actually discontinued in 2021). We were forced to make this change because users kept getting hacked or setting up phishing sites, which resulted in the main heliohost.org website getting blacklisted on places like facebook. Accounts that had one were allowed to continue using them until the domain was changed or removed, and when Johnny crashed, all such domains on Johnny were effectively removed.
It can be added back temporarily if there a specific reason you need this domain (for example we had another user for example who had embedded devices pointed to one of these...he had to release firmware updates to change the domain). Do you have a specific reason it's needed? If so, we'll add it back as an alias temporarily and set it to redirect to your new domain for you, but do keep in mind there will be a point where the .org domains will no longer work for regular users.