Metronome weirdness

Hi folks,
 
I have been having a metronome problem with a project today, and its really frustrating. I used the audio metronome to lay down some basic tracks for a new project, then turned it off to record some additional tracks. Then tried to turn it back on to record some others. No sound. It was definitely working before, but now the metronome was silent.
 
I've checked all the parameters in the metronome settings, and everything is at its default setting, and it should have been working. But nothing. The only thing I did during the time that the metronome was turned off was add in a new stereo bus for a reverb send. I didn't touch the Metronome bus, or change any other settings.
 
I did discover -- after some curse-filled and very random fiddling around -- that the only way to get the metronome sound back is to click on the rack menu in the reverb send, and select "Bypass FX Rack of this Type." Then, I could hear the metronome again, at least for a little while.
 
However, it stopped working again a few minutes later, and so I went back to the rack menu for the reverb send, and this time de-selected "Bypass FX Rack" and "Bypass FX Rack of this Type". And the metronome is working again.
 
I'm not sure that makes a lot of sense, but it's what is happening. If anyone has experienced this, or knows what detail or setting I am apparently missing, I'd appreciate it.
 
I'm using Sonar Platinum 64 updated to Kingston, ESI Juli@ PCI soundcard with latest drivers, Windows 10 Pro 64 updated (I think) to the latest patch, and the VS-700C console in USB stand-alone mode via the Win 8.1 drivers from Roland.
 
Rob