Sounds like issues I've seen that that I recall "solving" by simply 
disabling NetworkManager.  Iirc, there is a driver for some Intel 
interfaces that is known to sometimes take too long to do some 
initialization step that causes NetworkManager to keep resetting the 
port (or something like that - don't have time to consult the Google 
just now to find it again).  The upgrade may have caused enough change 
in that initialization step to exceed NetworkManager's timeout.

Hope that helps.

On 1/6/2021 4:29 PM, Larry Linder wrote:
> d one of our boxes from 7.6 to 7.9 and no network connections.
> Looked at Ethernet connection and no lights.  Unpluged the cable and
> plugged it back in and you could see lights and then they went off.
> After tripple checking everything I could think of we rebooted to 7.6
> and presto it all worked.
> Something in 7.9 turns off the Ethernet port !!!! or the driver in 7.9
> is hokey.