This problem can stem from both the blender or even the circuit powering it. First ensure that the outlet you have your blender plugged into is powered and not "tripped". Most kitchens have what are called GFCI outlets that can trip and cut power to appliances. Once you are certain your device is receiving power, remove bottle and blade assembly; then depress the two black micro-switches inside the base of the blender. If your blender still won't turn on then you may have a faulty motor or motor connection. Also, refer to the My Blend Troubleshooting Page.
This problem can have a few sources. Either the seal is damaged in the blade assembly, the bottle is cracked, or the blade assembly is cracked and requires a replacement. For more detailed answers visit the Oster Blend-N-Go My Blend troubleshooting page: Oster Blend-N-Go My Blend Troubleshooting