Connector sender instance can connect, but receiver keeps saying "NOT CONNECTED"

When the sender can display the name of the receiver, the connection is fine. If the receiver instance still displays "NOT CONNECTED", it means that the host application is not streaming any audio or midi thru the plug-in.

In most host applications (such as Logic, Cubase, Cakewalk, Pro Tools, Studio One, Ableton Live...), you will have to activate "input monitoring" on the track of the receiving instance so that audio and/or MIDI goes thru it.