I had this same issue when I bought the flush from you last time. Had VM drop out and after much work got it going again. The printer was working fine up to this point.
I had heard that there is vacuum needed to help pull the ink thru the head, during a cleaning? I am wondering if for some reason I don't have adequate vacuum to pull the ink thru.
The flush is going thru to the waste tank. At least the screen on the computer shows less capacity available in the maintenance tank.
Originally, I had total drop out on VM and 10 or so nozzles in Cyan that weren't working. Once I ran the flush thru the system the first time, and let it sit overnight, I got all of Cyan back and a few VM back. I ran the flush one more time with the exact same results.
The humidity in the room had plunged to 30% before I caught it, which caused my original problems. Now it is up 45%.
With the service program, the selection I used was the ink charge for the one pair Cyan / VM. Not sure of it would help to run the full side charge of the clean lines option?
I'll keep playing with it, if I get any results, I'll let you know. Yes, the 4900 is a pain, when it goes down. Beautiful when it prints.