XPS 9570 problems

Hello, so I've bought an XPS 9570 on eBay to replace my 9550 and I was so excited until I started working with it...

So far, my main problem is turning on... Sometimes it takes several attempts to turn it on, other times it just turn on if it's connected to mains even with a full battery...

Additionally, I can't figure out how to make the fingerprint scanner work...

On top of all, considering I bought it from the UK and I'm in Portugal, I'm trying to transfer the ownership to here but Dell website doesn't recognize my service tag, even if all dell software does...

Any advice?

Thanks