If the blender jar is incorrectly assembled, this could cause it to be locked to the base (motor unit).
In order to solve this, please follow these steps:
1) Unplug the blender.
2) Open the lid and remove the ingredients from the jar.
3) Hold the handle of the blender jar, lift it up and turn it anti-clockwise at the same time.
4) The blender jar will be released.