HI Turnej,
Welcome to Apple Support Communities. We understand that you're having some issues using your USB-C to Headphone Jack Adapter.
First, make sure that the issue isn't with your headphones by testing another set of headphones if possible.
If you find that this adapter is not working, it may be best to contact Apple or the retailer where the adapter was purchased. You can reach out from Get Support or using the direct phone number for your region from Contact Apple for support and service.
Take care.