NIC goes dark when Proxmox kernel loads after GPU install (works again if GPU removed)

Like the title says. I installed a GPU, everything posts and boots fine. The lights on the Ethernet port are lit up and will stay lit up indefinitely (I assume) if I leave it at the kernel select screen.

But as soon as I load a kernel, the lights go dark. It also is not shown as an active client on my gateway, so it’s not working at all.

I’ve tried lots of commands I’ve found to force it up. It looks to me like the NIC assigned to vmbr0 is correct. Etc. I just can’t get it to work.

If I remove the GPU, it immediately works again. NIC stays up after the kernel loads and I can access the web UI as normal.

rooteprox. *

root@prox:*# ip a

1. 10: «LOOPBACK, UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
   link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
   inet 127.0.0.1/8 scope host lo
   valid_lft forever preferred_lft forever
   inet6 :: 1/128 scope host noprefixroute valid_lft forever preferred_lft forever
2. enpsso: ‹BROADCAST, MULTICAST> mtu 1500 qdisc noop state DOHN group default qlen 1000 link/ether a8:a1:59:be:f2:33 brd ff:ff:ff:ff:ff:ff
   enp0s31f6: «NO-CARRIER, BROADCAST, MULTICAST, UP> mtu 1500 qdisc pfifo_fast master vmbro state DOWN group default qlen 1000 link/ether a8:a1:59:be:f2:32 brd ff:ff:ff:ff:ff:ff
   vmbrO: ‹NO-CARRIER, BROADCAST, MULTICAST, UP> mtu 1500 qdisc noqueue state DOWN group default qlen 1000 link/ether a8:a1:59:be:f2:32 brd ff:ff:ff:ff:ff:ff
   inet 192.168.1.3/24 scope global vmbro valid_lft forever preferred_lft forever

root@prox: *# cat /etc/network/interfaces

auto lo

iface lo inet loopback

iface enp0s31f6 inet manual

auto vmbro

iface vmbro inet static

address 192.168.1.3/24

gateway 192.168.1.1

bridge-ports enp0s31f6

bridge-stp off bridge-fd o

iface enps0 inet manual

source /etc/network/interfaces.d/*

root@prox: ~# service network restart

Failed to restart network.service: Unit network.service not found.