why my avatar always in sit down position ?

[Rolig Loon]

Sometimes a scripted animation can fail to stop when you leave it.  That's especially true for dance machines and the pose balls in some seats and vehicles.  You can usually stop the animation with  the Me >>> Avatar Health >>> Stop Animating My Avatar menu in your viewer.  (There are many different names for the menu in different viewers, but it is always in the upper left corner of your veiwer screen.  Look for it.)  You could also use a Magic Wand device.  Many of them are available for free in world or in the Marketplace.

[Rolig Loon]

Sometimes a scripted animation can fail to stop when you leave it.  That's especially true for dance machines and the pose balls in some seats and vehicles.  You can usually stop the animation with  the Me >>> Avatar Health >>> Stop Animating My Avatar menu in your viewer.  (There are many different names for the menu in different viewers, but it is always in the upper left corner of your veiwer screen.  Look for it.)  You could also use a Magic Wand device.  Many of them are available for free in world or in the Marketplace.

[Darya]

Are you using an Animation Override for your avatar? If so, there is a button called "Sit Anywhere" and perhaps you have clicked on that one by any chance? Check your AO (Animation Override) and see.