The Information Server contacts the StWatchdog.exe on the Normal Server via port 5169. The watchdog listens to this port for any Information Server request. If the firewall blocks the port, the Information Server will fail to connect to the Normal Server.
To resolve this issue, make sure to open port 5169 on the firewall.
This issue can also happen when the Trend Micro Serverprotect Service (spntsvc.exe) is manually stopped. When this happens, the spntsvc service notifies the watchdog to also shut down therefore the Information Server will not be able to connect.