Cannot get ethernet to reconnect after connection loss

I have a server that running Ubuntu 22.04.4 LTS - I have upgraded between LTS releases a few times, and the server is probably a decade old. I'm not sure when it happened, but somewhere along the way, it stopped reconnecting after connection loss. I'm wondering if you fine people can give me a hand diagnosing it.

ip a lists a lot of devices, but the important two (I think) are br0 and enp1s0. The onboard nic stopped working years ago so I disabled it in the bios and switched to a PCI nic:

01:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 15)

Anyway, I can manufacture this problem by unplugging the Ethernet cable and plugging it back in, but when my ISP goes down, the same thing happens. Once the connection is lost, I can't get it back without rebooting.

I've tried the following on both enp1s0 and br0

• sudo ip link set DEVICE down and then sudo ip link set DEVICE up
• sudo systemctl restart systemd-networkd.service

But none of these commands seem to reestablish the connection. Anyone have any idea how I should start diagnosing this? I can repro on demand and get logs, etc.

Thanks in advance,