Hello.
Which connection type did you choose, FSUIPC or Simconnect?
Do you have the latest version of FSUIPC installed?
Start FSX and FSrealWX with admin rights.
If you find an error, then please give me exactly about your system. Which sim (FSX / P3D / Xplane). Which connection (FSUIPC / SimConnect / FSrealWX-Bridge). Which OS.