EmonPi - no ethernet connection

My EmonPi has developed an issue after some rather extreme weather which produced some hitherto not experienced snow ingress.

Sequence of events:
Thursday morning the EmonPi was found powered down with evidence of some snow ingress around the board it is mounted on. I can not say for sure how much snow although it looked like only a very light feathering. Precisely where it had made contact with the Pi is also uncertain but most probably on the face where the Ethernet socket is as this faces up. I also can not say whether there was a short anywhere - on the Pi or simply on the power socket supplying it but the CU breaker for this had not tripped. Note that the Ethernet connection is via a Power line set-up (BT units) - not ideal I know but the Pi is situated in outbuildings 20+m from the house and this arrangement has worked ok for a couple of years. It is possible the powerline plug also had contact with snow.
I disconnected the power supplies and “dried out” the Pi and associated equipment over the next 8-9 hours. I did not open it up.
When I attempted to restart the boot-up sequence stalled. I reset and repowered it and it went through the boot-up sequence ok. All inputs etc are ok and can be cycled through on the LCD but no Ethernet connection is displayed and there is indeed no connection. I have reset in the standard way several times since with the same result. The EmonPi seems to be operating correctly in all respects other than Ethernet connection although I obviously can not confirm that without being able to communicate with it! The powerline units seem to be operating normally.

I am strictly a user not a developer and am wondering about my simplest way forward. Is this just a hardware problem or could there be an issue with the SD card? I would need to disconnect the EmonPi completely to physically work on it which I am loath to do unless necessary as the CTs etc are not readily accessible. I do not have the means to connect to the Pi locally.
Note I upgraded the EmonPi using the UI button about 10 days ago without incident. There are a couple of TXs in the system which still appear to be working ok (LEDs flashing normally). Everything was shop sourced and has not been modified in any way. This is an off-grid system and the Pi CTs are monitoring PV and Wind generation.
Any suggestions for a relative numpty where these things are concerned?