New Sony WF-XB700 headphones do not turn on despite charging

[Achakzai]

Hello,

I bought online New Sony WF-XB700 headphones from out of Europe and now they do not turn on from the beginning fully despite charging.

The problem is that I bought two sets of Sony WF-XB700 and both have the same problem. 

Please guide me how to claim its Warrenty here in Germany since they can not be returend to the seller. 

thanks