@drmac, @charterali, @alphaX, Racerf1
Thanks guys. Oil has been changed twice in last six months, last gear oil change was less than a month ago and mechanic also cleaned filter. But same again.
Engine revs and vehicle moves, say for 400-500 meters, when I see that revs goes up to mark 3 but still it does not change the gear. One short term solution I found is take the gear back to manual mode on position 2, where it gives a shoot.
Now as Racerf1 said to change clutch pack, valve body and filter, seems no other option if this is the only solution.