RAX120 ssid not picking up

Nothing like enough detail there to diagnose by remote control.

What firmware version do you have on the device?

A number is more useful than "the latest". (It may not be by the time people read this.) There can also be newer versions, or "hot fixes", that do not show up if you check for new firmware in the browser interface.

It might also help if you told people what the modem is in front of this router. The model number could be useful. Is it, by any chance, also a router, with a set of LAN ports on the back?

The reason for asking is that a lot of people turn up here trying to put a router behind a modem that is also a router.

You can help people to help you by providing the information suggested in this forum's header:

Subject (Include model number and brief summary)
Model (Recommended - Helps the community give the best answers)
Body (Include additional detail including model version, firmware, OS and environment where relevant.)

They are there for a good reason.