Dokuwiki behind SWAG reverse proxy report 502 Bad Gateway

I installed dokuwiki docker with SWAG in a same network. at the sametime, I removed suffix sample from dokuwiki.subdomain.conf, I tried to access it from browser like, the browser report 502 Bad gateway.

I tried to connect to swag terminal, tried nslookup dokuwiki, it shows it could found the right IP of it.

Here I don’t know what the next step how to solve it.

Could someone help to give me some guidance for it?