Recent versions of macOS are getting more and more picky about unsigned executables downloaded directly from the internet. It could be that the execution is denied because of that, however your question is not specific enough as it does not state whether this occurred when you start the configuration, or during building the simulator or when running the IDE.
Temporarily you can turn off the developer identification. See this article:
See this article. On long term, OMNeT++ distros should be signed.
ps: I'M also assuming that you are running on an Inter processor based machine. (arm macs can also run omnet, but there is some trickery to do before that is possible)
与恶龙缠斗过久,自身亦成为恶龙；凝视深渊过久,深渊将回以凝视…
