Hello and welcome to the forum 🙂
Unfortunately, we have no guide on how to setup REI3 behind a NGINX reverse proxy, but I´ll try my best.
Does REI3 use the SSL cert or is the proxy frontloading the HTTPS connection and talking to REI3 via HTTP?
We´ve had a community member that also used NGINX as proxy - here is the appropriate post. It might be helpful.
