twisted,
neutral light flashing probably means the seat switch is not made or if the seat belt system is tied into the drive that circuit is not closed.
The truck is designed with an operator presence system so it sounds like it thinks your not on the seat when you select a direction so the neutral light blinks telling you something is wrong in that circuit.

hello I have a P33000 ser:T39A10033 with neutral light blinking can anyone tell me what causes this to happen and how do I fix it? I have no error codes

first off a complete serial number of the truck would be helpful :o)