I had 2 working partitions. After Netinstall failed to install twice, I was left without OS on the router.
I spent hours trying to get Netinstall to detect the router again, until I found a post saying that the ports get corrupted and you have to reboot the PC. I did it, and it detected the router immediately.
I found another post after much searching that said to try with an ethernet dongle if Netinstall fails to install. What I had was a Thunderbolt dock with an Intel controller. It just worked.
I had to use Netinstall because upgrading from the router would not work, it would stay at the same version after reboot.