I've had my 300 for several years, but just got Workbench today.   I've read through about 5+ threads on the same topic and I cannot get this to work.   The workbench USB interface is 'green' and is seen by Monkey...it can update and reinstall the firmware, etc.   However, workbench cannot communicate with the 300, it just blinks red on that side of the interface.   I have the XPS and I'm running on XPS rather than battery power.  I also have tried moving the workbench interface to every USB port on my Mac Mini with no luck.   I tried 3-4 different Ethernet cables in addition to the cable supplied with the workbench interface.  No luck. 

I notice that when I disconnect and reconnect the TRS connector from the XPS to the 300, briefly the workbench interface goes green, then blinking red again (on the Variax side).   I also notice that if I barely insert the TRS connector into the 300, I can get the green light on the Variax side of the workbench interface to stay green.  But, when I launch Workbench in this state, it can't connect.  Inserting the TRS connector all the way into the Variax causes the light on the Variax side of the workbench interface to briefly show green, then blink red.   This would lead me to believe that there is some signal going between the Variax 300 and the workbench interface...at least in one direction. 

I have looked at all the pins on the workbench interface and the guitar...all 'look' good.  Nothing bent..no pins are too low to make contact.

Shy of replacing the internals and guts of the 300 or the Workbench interface, anything else I should be trying?   I know someone else had luck on ordering a new connector assembly for the 300.  I don't see that available in the store.  Any other ideas?

Ryan