This plugin will only work for clients which connect to the server via certain server browser tabs, as the use of the redirect command is restricted on that basis. It will not work for clients who connect from the Internet tab or Quickplay, Quickpick or the like.
Hence, this plugin is essentially a down-grade over the previous system until those deficiencies are addressed. One way you could get around it is by querying the client cvar cl_connectmethod when they select an option. If it's a method that supports the new redirect command, then redirect without a prompt. Else, use ask for redirect. (Unless I've missed the fact that ask for redirect has the same restrictions, which I don't recall it having, in that case accept my apologies)