1. Communication setting error: Make sure the communication settings between WinCC7.4 and Broadcom simulation are correct, such as IP address and port number.
2. Firewall settings: Firewall settings may prevent communication between WinCC7.4 and Broadcom Simulation. Please ensure that the firewall allows communication between the two softwares.
3. Access rights: It may be that the running users of WinCC7.4 do not have enough access rights to access the Broadcom simulation software, resulting in the inability to establish a connection.
4. Incompatible software versions: If the software versions between WinCC7.4 and Broadcom Simulation are incompatible, it will also lead to connection problems.