Dear friend!
1. If two PCs use the LCT to log in to the NE at the same time, use different accounts and passwords.
2. If you log in to the device in different time segments, check whether the account and password are correct. Before login, you can use the ping test function to verify the connection between the PC and the NE.
3. Check whether the communication port is disabled because the antivirus software and firewall are installed on the PC running R021.
Thank you!