I finally got everything working today. Success! Not easy, but I persevered.
From the (very helpful) VST Connect In Depth site : “You can get mono if you create a Mono VST Connect Input channel instead of the default stereo one. So you may go to Devices/VST Connections/Inputs, delete the VST Connect Input channel, create a new Mono Input Channel and insert the VST Connect plugin there.”
How do insert the VST Connect plugin on the mono channel? Can you have both a stereo and mono input channel to choose between?