Hi,
Thank you very much for your kind words!
I tried to log-in and check, but neither the login or the plugin is visible on the page.
Usually I recommend going through this checklist if this error comes up. The error 400 is very rare response from the server, but usually indicates an issue with the firewall. The server does not like the request and might be blocking it.
I recommend checking on the firewall to see what it captured, as it may cause some problems in the future for something else as well.