If the legacy installer fails, try OBS Studio (free) or Camo Studio (modern alternative). But for the classic ManyCam feel? 4.0.52 is still king.
Here is a detailed breakdown of why you should avoid this specific version and what to use instead. download manycam 4052 for mac best
If you want to make sure this works for your system, let me know: What are you currently running? Are you using an Intel or Apple Silicon (M1/M2/M3) Mac? If the legacy installer fails, try OBS Studio