1. Customer feedbacked taht citrix license didn't expire.
2. We checked and confirmed that the name of license server was same as the HOSTNAME of citrix license file and license file was valid.
3. We asked customer to login Citrix License Administration Console and feedback screenshot to us, we found that there was no citrix_startup license in Citrix License Administration Console.
We asked customer to check whether citrix_startup.lic file existed in 'C:\Program Files (x86)\Citrix\Licensing\MyFiles' in license server. Afterwards customer replied that citrix_startup.lic file didn't exist(Refer to following screenshot).
After Customer copied citrix_startup.lic file to corresponding directory in license server and restarted license server, the problem was resolved.