Port Forwarding is not working AC-87VG

Hello,

First post here and not expert in these things. However, I know how to do a simple port forwarding for my BitTorrent client.

So, I have bought an ASUS DSL-AC87VG from ebay but port forwarding does not work.
I use the latest available firmware, and I have read all the related posts in this forum, but unfortunately had no luck.
I rolled back to previous firmwares, but no luck also!



Has anyone any ideas why this happens?
Is there any way to...

Port Forwarding is not working AC-87VG