Here for general reference, an email reply from the people who run the LVTC site:
The "you have been blocked" message comes up when a visitor triggers the website's firewall by doing something untoward, e.g. repeatedly attempting to log in to the admin area.
You get three chances before you're blocked for a day, and if you're blocked three times you get permanently blocked by the firewall.
To block visitors the firewall uses their IP address. Unfortunately, because IP addresses are usually shared that does mean some genuine visitors will also get blocked. This appears to have happened [name].
I have cleared the block lists, so [name] will have access. If he doesn't please advise him to clear his browser history (the same thing will apply to anyone else).
Going forward, I've revised the firewall configuration and changed part of the warning message to say:
"Contact [email protected] with your IPv4 address (visit https://ip4.me) if you believe you were blocked in error."