Today we found we cannot access to remote desktop (first attached picture).
Then we found the computer next to standalone cannot connect to network. Even after we restart the PC, it cannot connect to network. Second attached picture shows LAN cable connection to the PC.
[Matteo, Yuhang , Eleonora]
The problem was solved just by replacing the LAN cable that connects the desktop PC to the router. Note that the light at the LAN cable connection is still yellow/red and blinking. Probably it doesn't need to be green.