Have you connected the printer to the new modem/router via wifi? This is normally done via WPS (push button security).
Alternatively have you connected it via USB to the modem? I ask this because from memory the latest versions of the Gateway Max firmware were supposed to disable printer sharing via the USB port using the modem as a print server.
Alternatively have you connected it via USB to the modem? I ask this because from memory the latest versions of the Gateway Max firmware were supposed to disable printer sharing via the USB port using the modem as a print server.