If the function light is flashing, it could be caused by a couple of things:
If you try to switch the device on while it is connected to the charger. If so, take the device off the charging unit first before switching it on.
The cordless vacuum cleaner has gone into safety mode, because the battery has reached a high temperature. Unplug the charger cable and allow the VC100 to cool down.
If issue persists please contact customer service at 888-867-9375