Go through the procedure, but it will not help. The reason why I say that is that it is a uni captop and it cannot affect one channel totally. If top was failing, it would be across multiple channels (columns). The flushing might help move the air, if that, but you are pushing 4 channels to get to the fifth. All the best, document your steps so that you can be helped later if possible. Again, first step would be to check for air in the lines, the next would be to replace the damper.
That is the first step, the visual looking to see ink going into the dampers
Next, use a syringe from the pharmacy and pull from under the top until you get movement in all the lines
If neither of those work, then you have to think a failed damper
Great to hear, a bad cap does not target one channel, but it not seating correctly can cause it not to get the proper suction. Glad you are back up, Happy CAMMing!