Chainsaw Repair

Hi guys. Just taken into the workshop a near new (still on original chain) Stihl MSA220 with the AP300 battery. Battery all charged up, but chain motor not going and chain not rotating when operated. I thought it was customer using it with the chainbrake activated, so de-activated it and still nothing- just a high pitched and faint electrical weeeeee sound when switches depressed. Symptoms were still as if the chainbrake was still activated, so removed the chain cover and was pretty clean under there, so removed bar and chain and tried moving clutch sprocket by hand as was pretty solid even without chainbrake on. Got it to rock back and forth a few millimeters, then tried the switch again and the sprocket jumps forward for a millisecond and stops then you get this very high pitched electrical weee sound, as if the battery is trying to do its job but the locked sprocket is preventing it in doing so. Any ideas what could be locking the sprocket with the chainbrake deactivated? Not done one before so don't want to start taking apart stuff that doesn't need to. Thanks.

= Is it at a dealer? Should be a warranty.
By pass the switch see if it works then. But sounds like a bad motor or broken drive gear that's grinding

 MSA220 small service manual
https://www.mediafire.com/file/5xuz7158dd47ogr/MSA_220_sm.pdf/file

I did forget to add, the battery is fully charged and showing 4 green full charge bars when status button on the battery is depressed off the machine. When fitted to the machine it flashes 3 red bars.