Connect a computer to one of your router's LAN ports using a CAT (Internet) cable, then go to 192.168.1.1 using your browser. That should take you to your router's setup page.
Login / password might be user / user, or you could try cht / chtnvdsl or cht / chtnadsl
If you can login successfully, you can see if the wifi setting is turned on. If it's on and you get no signals, chances are your router is kaput.
If you could log in to the router, and you know your PPPoE password, there is a reset button on the box. Try pushing it for 10 seconds, and log back in and configure your PPPoE and wifi settings. If that still doesn't work, you need to get the CHT guys over to replace the old wifi router.
You could also forget CHT's crappy wifi router, buy a standalone wifi router and connect it to one of your old router's LAN ports. Configure the new router and enjoy.