The WAN/DSL router seems stuck on DSL though switch on back is on WAN. ZYXEL P-2812HNU-F1 vT

My mother has an older WAN/DSL wireless router P2812HNU-F1 vT - the network is fine, already tested, fiber.
This happened suddenly after a blackout: When connecting the WAN cable to the router the NSP cant find the router. The Wireless led is blue, Power is red, DSL orange and the Internet red (WAN led is off). The WAN/DSL switch is on WAN and nothing happens when switched. I have tried several times to RESET the router and also swithing on/off power, disconnecting the adapter while RESETting, but the lights are stuck as above. Tee power led does not start blinking, just stays on red. Is this a hardware problem or what can be wrong?
Kind regards, Lena

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