I've been having problems with a stereo pair of the 500 series delays. Occasionally I see the yellow light that signifies a midi message, but for the last few days I've been able to get any midi communications working whatsoever. I've tried swapping, midi interface, midi cable and linking and de-linking the 2 units.
What is particularly odd is that I tried a firmware update using SysEx librarian - this worked perfectly which suggests all the connections are working as they should be.
Any help much appreciated!