Host has no internet after installing HA on official RPi5 NVMe SSD

I bought a Raspberry Pi 5 with the official NVMe hat and 256GB SSD to run Home Assistant.

I installed the SSD, put Raspberry Pi OS on an SD card and used Imager to install Home Assistant on the SSD. Which all seemed to work well.

My first attempt when HA booted up was to go straight in with restoring a backup from my current Home Assistant, which is on a Raspberry Pi 4. It sat there for a long time, until I was pretty sure it wasn’t doing anything. So I tried setting up HA instead, and restpring the backup from “inside”.

This is where I started getting errors about the host not having an internet connection, although it clearly has; I can access it from my Home Assistant Cloud account. Nor will it install add-ons, for the same reason. I’ve tried everything I can find online such as resetting the network from the CLI (it can’t ping anything from CLI either), setting a static IP address, changing the DNS settings, disabling IPV6, and checking the router wasn’t blocking anything. I’ve even tried the same SSD in a different Pi5 and NVMe hat, but it’s the same.

I’m a little out of ideas, and wonder if anyone had any thoughts? Thanks!