Grafana anonymous dashboard - Always redirected to login page

Hello , I am running a separate instance of Grafana with reverse proxy (nginx)
v8.3.4 (a551d74b11)
Ubuntu 20.04

Accessing and login in with “” works well.
I want to share dashboards and display them in my ipanels using anonymous dashboard sharing.

I also enabled embedding.

When trying to browse the url of the dashboard, it gets automatically redirect to the login page.
Any ideas why ?