1: Make sure proper database name is entered in the iVend connection manager.
2: Firewall should be off.
3: SQL server and license server should be on same machine.
4: Make sure SQL server name or IP address should be correct in license registry file, check the below steps for the same.
1: Press Window + R button. And then type Regedit press Enter.
2: Expand: HKEY_CURRENT_USER >> Software >> Click on FLEXlm License Manager.
3: Click on _CITIXSYS_LICENSE_FILE right panel and enter correct SQL server license serer machine name then press OK button. Then try to login in Management Console.