Firewalla Orange that was previously used on a Comcast network in Bridge Mode.

Hello Firewalla Support,

I'm trying to repurpose a Firewalla Orange that was previously used on a Comcast network in Bridge Mode.

Here are the steps I've taken:

Performed a hardware factory reset by holding the reset button for approximately 30 seconds.
Connected the Firewalla directly to a Nokia T-Mobile Fiber gateway using Ethernet (WAN only).
The Firewalla is isolated from my production LAN during testing. The LAN port is not connected to my switch.
The Firewalla obtains a DHCP address from the Nokia gateway.
The Nokia detects the Firewalla as an Ethernet device at 1 Gbps and assigns it an IP address (currently 192.168.1.70; previously 192.168.1.69).
The Ethernet link lights are active and blinking.
The Firewalla app can no longer manage the device and reports it as "Unreachable."
Before it became unreachable, every attempt to switch from Bridge Mode to Router Mode asked me to select the WAN port, spun for several minutes, and then returned to Bridge Mode.
Diagnostics consistently referenced "Bridge 1" rather than creating separate WAN/LAN interfaces.

Additional observations:

The Nokia detects Firewalla MAC addresses ending in ...FC and ...FD, suggesting both Ethernet interfaces are present.
The Firewalla status LED is currently off, although the Ethernet link remains active.
The device was originally installed on a Comcast network by another phone, then factory reset before being moved to the T-Mobile network.

Could you please advise:

Is there a recovery procedure if the Firewalla management service becomes unreachable after a factory reset?
Is there a known issue preventing the transition from Bridge Mode to Router Mode?
Is there a way to verify or reinstall the Firewalla software if the device is reachable on the network but unreachable from the app?
The Nokia gateway detects the Firewalla at 192.168.1.70 over a 1 Gbps Ethernet connection, but the Firewalla app reports the device as unreachable after a hardware factory reset.

Thank you.