PLCSIM V5.4 SP8 is not officially supported on Windows 10. However, many users report success using Windows 7 compatibility mode or running it inside a virtual machine (VMware or VirtualBox with Windows 7 guest).
If your PLC won't connect, check the "Set PG/PC Interface" settings. Ensure the access point is set to "PLCSIM (MPI)" or "PLCSIM (Local)". simatic s7-plcsim v5.4 sp8 download
Siemens provides official trial software for S7-PLCSIM V5.4 SP8, which includes all subsequent updates. PLCSIM V5