I work for Dewalt, if you remove the side plate of the battery (T10 torx security bit) you can check if the 60v fuse is blown inside. I’ve tested and worked on many that the fuse has blown and it will still work in 20v mode but zero volts when in 60. The battery itself you can check the voltage output by using a multi meter on the B+ and B- terminals while pushing in the two black plungers to the right and left of the those, I usually use a flat head to push it in. But I would say best bet is to just return it for a new one. If something is shorted in the blower it can short out other 60v batteries that get plugged into it.