Unfortunately, I have no idea what you are doing and where it goes wrong. That makes it impossible to even guess as to what is going wrong.
"No access to WiFi" isn't enough detail.
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, if there is one. 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. That can complicate troubleshooting.
Apologies for all the questions. But 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.)
