Good afternoon, I have the same problem but with an H300HD forklift.

how did you solve the problem

Can you help me find the fault?

Luis,

There could be a number of reasons the hydraulics cut out. What style of attachments are on the mast? Some will have proximity sensors that will fail, and hydraulics are locked out. I doubt this since you can turn off and back on and have hydraulics for a short time. I would suspect a failed connection in the estop switch, a malfunctioning priority valve or seat switch wiring issues. You can try calibrating the hydraulic handles. If you have single levers, disconnect the harness where they all connect with switch on, reconnect the harness and move each lever in forward position and hold for 3 seconds. Then move in opposite for 3 seconds. Complete this for each handle then shut lift off. Should you have a joystick, do the same thing, only you will have to complete each function, holding in each position for 3 seconds. Since you have no codes i do not know what else to suggest. One other thing, if it is in a cold environment, the hydraulics need to warm up before operating any functions. Thanks.