1. Capture network packet on IP phone side, and found IP phone already sent out subscriber message, but received a “500 internal error” message from U1980.
2. Check U1980 logs, and found U1980 think “the user does not have the newservice” then send 500 message to IP phone.
3. Check the user rights on U1980, this user already have BLF services.
4. Check other service of this user and found this user have One Number Link You (ONLY) service, but the main number didn’t open BLF service, when there is a ONLY service opened, the system always check the main number’s service rights.
5. Open the main number BLF right, the issue was resolved.