I'm not a customer so I can't help much, but you should start with digging up your contract, if there is one. Is there anything that you signed/clicked on/etc beyond the horribly formatted "Terms": https://btclend.org/Landing/terms.html

Do you have any contact information for BTCLend LLC or any of its principals, other than e-mail addresses?

Depending on the size of your loss you might want to talk to a lawyer but your chances of recovering anything are probably very slim.