Hi @lmr880 ,
HTTP 502 Bad Gateway error most typically indicates that the Portal (probably reverse proxy or web adaptor) cannot reach "https://test.com".
First, I would check whether the web adaptor or proxy server could reach "test.com" and make sure WebContextURL is configured correctly on the Portaladmin endpoint. Also, you might want to check the SSL certificate for "test.com", if it's self-signed and trusted or not.
If your portal machine has access to the "test.com" you might check if you can access the "test.com" directly through the internal port (7443) of portal. You can use a URL like this: "https://<portal-mac-name>:7443/arcgis/sharing/checkurl.jsp?url=https://test.com"
Hope this helps.
