I created new scene and made a simple tree using navmesh but still the speedchange is not working. can you please check from your end.Hmm, can you place a breakpoint within StartStopMovement ability to determine why the speed change ability isn't starting? To make things easier you could create a new tree that just uses the Start Stop Ability to determine if it is something else within the tree that is causing the problem.
@Haytam95 Thanks it worked if i keep it like this is it ok?@Maximuz24 "Always return success" may be creating a false positive and the ability isn't starting.
Speed change requires the character to be in movement, in the first frame it's not, so the ability won't be able to start. And because you don't have a repeater, the sequence will be only executed in the first frame.
To make a quick test, in the Speed Change ability unselect the checkbox "Requires Movement".