Sorry for my late Answer I start to write a manuell here: Support for Easybox 904 LTE
If you have concrete question you can ask here.
I recoment to open the box an connect via serial-UART-usb-adapter for seeing what is going on.
exist questions to the connect via serial discription here https://openwrt.org/toh/astoria/arcadyan_astoria_easybox_904xdsl_r01 ?