If your V12 is not feeding there could be a power, magazine, alignment, timing, or mechanical issue. Always point the rifle in a safe direction, and always wear eye protection. Then check for these issues:
Is the battery dead or not fully charged? A low or dead battery will not provide enough power to cycle the engine completely.
Do you have enough air in your tank and is the output high enough? Too low of an output may cause the engine to not fully cycle.
Is the magazine feeding fast enough? If the gun feeds and shoots fine in semi or at lower rates of fire than the magazine is likely not feeding fast enough.
Is there an alignment issue with the nozzle and hop up? Because every receiver and hop up have slight differences the nozzle may not be able to smoothly go in and out of the hop up. Damage to the nozzle will indicate some friction that could be causing the feeding issue.
Is the bolt dwell set high enough? Try doing a factory reset or if dynamic timing is turned off try turning it on and set your desired bbps and try it. If dynamic timing is on, try turning it off, and then increasing the bolt dwell significantly and try it.
Is the nozzle moving at all? Remove the upper receiver and check if the nozzle is moving after each shot. If it's not moving or not moving far enough back, and you ruled out a power and air source issue, then there could be a mechanical issue.
Are both solenoids clicking? If you pull the trigger and listen to the solenoids while there is no air attached you should be able to hear both solenoids click. If only one clicks you know you have a bad solenoid. If both click there may be a clogged air line preventing air from getting to the nozzle chamber.
If the engine is still not operating correctly contact Valken customer support. Please open a ticket with our customer service department. To open a ticket, please click on the chat button on the bottom of this website and our customer service representative will be happy to assist you.