How to bring the Wi-Fi module of the router back to life?

Question

network hardware

Hello ! Literally 10 minutes ago I encountered such a problem - Wi-Fi stopped working on the router (ECI B-FOCuS O-4G2PWM). Communication via optical fiber. The first thing I thought about was that maybe the Internet payment was overdue, but it turned out not to be so. The phone is not connected to the telephone line, but to the router. The phone works, but cannot call some landline numbers (I don't know why). The WLAN light on the router is not on. Internet via ethernet cable works.
How can I diagnose a Wi-Fi module? How can it be brought back to life? Maybe it's still worth replacing the part or the router itself?