I purchased William-8kHz and got an email with my key. It indicated that I must enter the info "exactly" as shown in the email. No problem on my name and company name, but the voice name in the email was:
"William-8kHz for Linux (v5.x)"
Typing that does not work. Typing "William-8kHz" worked.
Thought i would post this in case someone has the same problem. :/