1.when i access https://portalname/rdweb i can log on using 443 port and access one of the RD Sessions
Are input this url into the web browser? If not kindly confirm the detailed steps you've performed.
Such url of Rdweb is used to for users to remote via browsers.
2.For normal remote connection starting from mstsc or Remote Desktop Connection Client, the Gateway setting is different thing than the target server you would like to access.
The computer here refers to the remote/target server that you would like access.
To configure RDGateway, go to Advanced-->Settings:
Checking bypass option will guide the remote session not go through gateway for internal network.
Hope this helps and please help to accept as Answer if the response is useful.