502 Bad Gateway on /admin

I read all topic about similar problem but i don’t fond solution.

I make a fresh install on a Rocky linux 8, install docker engine and docker compose and make install of bitwarden with : ./bitwarden.sh install

https://bitwarden.my.domain.fr works
but https://bitwarden.my.domain.fr/admin doesn’t work i have 502 Bad Gateway nginx
and in the nginx log:
2022/02/10 13:49:03 [error] 44#44: *246 connect() failed (111: Connection refused) while connecting to upstream, client:, server: bitwarden.my.domain.fr, request: "GET /admin/ HTTP/2.0", upstream: "", host: "bitwarden.my.domain.fr"

How can i solve this problem?