Dual Control Lever Problem - Shimano ST-M765
I need help.
I have a brand new, never used, Shimano ST-M765 dual control brake lever that, according to my LBS, "will not pump the fluid." They say that when they add fluid to the lever they can not bleed the line because the fluid doesn't go anywhere...ie. it is blocked somehow. Apparently they have tried everything -- even attempting to bleed the brakes in reverse -- from the caliper to the lever. They have determined that the caliper (Shimano M525), also brand new, is fine, and that the cables are fine. So they have narrowed the problem down to the lever.
I do not completely understand the way these brakes work, but I'm having a hard time understanding how exactly the lever could be blocked, plugged, etc. I am at a loss.
Anyone have any experience with these levers, or seen a similar problem?
Thanks in advance.