Try to register.
I tried like 10 times and each one got an error “Human verification error” though I’m sure i’ve entered at least 5 times the right numbers.
Maybe a Recapcha would be a better security method?
Have you also tried on a different server, or just 10 times on the same server? It’s possible it’s a problem only on sysad, but then you would need to contact the admin of this specific server, we can’t help anything with that. There is a contact link in the footer.