managesieve server not answering?

Trying to connect to managesieve server configured to port 4190. No go.

Roundcube is configured (thunderbird apparently having nothing current), but selecting "Add Filter" (new since re-configured for managesieve) produces "unable to connect to server".

Port 4190 does not seem to answer or be "bound" to anything. Telnet to 4190 produces "connection refused".

A "one box" solution.

If I had to guess, I would guess, operator error.    Otherwise, things are looking up.  But, I remember a movie that said never to do that . . .