Need more information!
Is the printer converted to a DTG or is it still a printer?
Is it just one channel or all channels?
What type of cartridges are you using? If you are using refillables, you have to make sure the rubber stopper is pulled from the vent side otherwise it will vacuum lock and the ink won't flow. The same for a CIS system, you have to make sure the vent side of the tanks are uncapped or it will vacuum lock.
On my R230, I had this same problem and it was due to a blown transistor which led to a blown fuse on the main board. Everything performed like it should but no ink came out. After replacing both components on the main board everything was fine.
If you are using cleaning cartridges in all slots and doing a nozzle check, unless you tint your cleaning solution it is very hard to see the solution in just a nozzle check since it puts down very little ink/solution.
You can purchase the Printer Jockey software which supports this printer. This allows you to flush an individual channel. At high resolution, it puts out enough cleaning solution to clearly see it if it is flowing correctly. I use this software daily to check and run an all channel low res flush.