FORCE_HTTPS=true is not working

[carlxo]

I'm running Koel with FORCE_HTTPS=true set in my .env but can still reach the WebUI through http://(localip):(port).

When I try to reach it through my reverse proxy (nginx) i get:

Mixed Content: The page at 'https://<url>' was loaded over HTTPS, but requested an insecure manifest 'http://<url>/manifest.json'. This request has been blocked; the content must be served over HTTPS.

Am I missing something?