Received non-functioning patient monitor although photos from last week were ok

Hi,

I have ordered a patient monitor from a German (I am also German) seller that has 100% rating on eBay.

He sent me a photo from last week that shows that the monitor was working fine.

Today it arrived, I turned it on and it did not start, screen just remains white indefinitely.

Actually I had a good impression of the seller and he has only good reviews.

So how do I proceed with this?

Thanks