No connection possible

I use a AX 1800 for while. Haven t been online with it since 12 weeks, now I try to connect again but none of my devices can connect to it. Not with or with the app on my mobile, which used to work just fine. Always say a connection is not possible, switch of the router and restart the Wlan. Tryed it a couple of times wit no success - any hints? Is there a way to do a “factory reset”

Reset: Repair or Reset - GL.iNet Router Docs 4

If this does not help, try debrick: Debrick via Uboot - GL.iNet Router Docs 4