Possbile reason：
1. The Console server IP address is not configured on the voice server.
2. The voice server IP address configured on the Console server is incorrect.
3. The attendant and attendant group information is not configured on the voice server.
4. The voice server license expires or is unqualified.
Solution :
1. Log in to the voice server and verify that the correct Console server IP address is configured.
2. Configure the correct voice server IP address on the Console server.
3. Log in to the voice server and check the attendant and attendant group information. a. Run the show telephonegroup command to verify that the attendant group information is correct.
b. Run the show telephonegroup groupno 0 command to verify that the attendant information is correct.
4. Run the show license command on the voice server to check the voice server license information. View the CTI users option on the voice server, compare the number of available CTI users and the number of used CTI users, and ensure that the former value is greater. If the license is invalid or unqualified, change the license.
