RBwAPR-2nD&R11e-LTE lost

Hi,
I have a RBwAPR-2nD&R11e-LTE that after a package update has been lost (not responding to old IP, not assigning new IP using DHCP).

I tried to run netinstall, but it seems not connecting to the netinstall software. What can I do? What is the EXACT procedure to put this device on netinstall mode?

thanks