You have your Speed and Position Icon operators *both* set to continuous.
It's not that particles are stopped, it's that you're resetting their position every frame...so they never travel further than the distance they can travel in one frame...because they're sent back to their starting position each frame.
It's not that particles are stopped, it's that you're resetting their position every frame...so they never travel further than the distance they can travel in one frame...because they're sent back to their starting position each frame.