Self hosted LoadBalancing server shutdown automatically

I use Photon-OnPremise-Server-SDK_v4-0-29-11263 with 'Free.100-CCU' license to host server and all firewalls are turned off. For business limit, we have no internet environment, server pc is wired to the router and other pcs are wireless. GameServerIp is set to local network ip.

Here're some steps to reproduce this issue:
1. Start LoadBalancing server as service, not connecting any client to it. After some period of time, the server shutdown automatically.
2. Execute 'Run Testclient' from PhotonControl, clients are able to hold connection for a short period of time(about 15s). After that, all the test clients' connection are forcibly closed by the remote host and finally the server shutdown automatically.

Does anyone know how to solve this issue?

Thanks a lot.