Hi there, after much investigation I have found the issue but it cannot be resolved sadly.
In the process of my troubleshooting I had to resolve a few account issues including suspending the account to see if this would fix the error message but it did not. The account then was reset which also didn’t resolve the problem.
In the end the account has been deleted fully and the data has been migrated for you to a new account under the same email address but without the full stop in the middle, a password reset email has been dispatched to allow you to login to the new site - https://tbbaltavistacom.000webhostapp.com/
On the new account I am able to park the custom domain but with the error message already in use - after various checks to your IP it would appear that you’ve a few accounts and one last month was suspended for exceeding the free plan limits, this domain is sadly tied to that suspension and cannot be reused on our free learning plan.
Feel free to continue to host your website with us without the custom domain, should you wish to use the custom domain you can migrate to Hostinger.com with ease!
If that is not satisfactory to you then you might want to consider alternative free hosting.