The main network cable is disconnected. Check whether the crimping method of the crystal head of the main network cable is wrong, replace the crystal head and crimp it again, or replace the network cable.
2. The signal of the main network cable is connected, and the signal indicator light of the receiving card flashes normally. It means that there is no correct RCG loading file in the receiving card. Open the display settings and load the correct RCG loading file.