Anyone getting a 406 error is not being blocked or blacklisted by Ring. All HTTP 4xx errors are considered client side errors. This does eliminate the possibility that changing a Ring server setting may correct the error but you are not being blocked or blacklisted and it us unlikely Ring can do anything to correct it.
A 406 error indicates the server returned a response but the client rejected it. You are getting to the Ring server. It is processing the request and returning a response. Your local client, or possibly a VPN server or your ISP’s servers, is rejecting the response from Ring.
Common causes are the client expecting a specific language or content type returned and the server returning something that is not expected. This could be as simple as the client expecting English but because of the location or configuration of the VPN server or the ISP server relaying the request, Ring is returning another language and your client, or one of the servers between you and Ring, is rejecting it.
406 errors are difficult to resolve because the end user’s client is not directly connected to the host server and the error can be coming from the end user’s client or any of the servers between the end user and the host.
I doubt Ring would be able to determine why and correct it. It is most likely not an issue on their end.