I just bought a new 21 inch mower (non-self propelled) this morning. Charged the battery as directed and inserted into mower. Started mower up and it runs for 5-10 seconds then stops before even starting to cut lawn. Power indicator on mower flashes Amber to green over and over. I wait then start again it starts right up then stops again with same blinking light. Already ckecked the clips and there is no debris underneath since it won't run long enough to start cutting grass. Any help would be greatly appreciated.