/smartlock{smartlockId}/auth

Hello!
I want to give access to people to a certain smart lock, therefore I am calling the /smartlock{smartlockId}/auth endpoint.
However I am having problems when making this call. I get the error “400 Bad Request”.
What could it be?

what is in the response body, maybe there is a hint?
what is in the request body and what kind of HTTP request are you sending (PUT, POST)?