When you start a stream, with TVHadmin or the TVH UI, a .m3u file is downloaded which your browser then passes to your player to open. The URL in the file from the TVH UI includes a 'ticket' parameter which links to your user credentials, the one from TVHadmin does not.
The quick workaround is to remove the need for authentication when streaming, by giving the "*" user basic streaming rights. I'll check where the 'ticket' comes from, and if it might be possible for TVHadmin to supply one.