The computer's USB system is the limiting factor for this, as each additional camera will use extra bandwidth and require extra CPU processing to maintain the connection.
Normally between 20 to 30 cameras can be connected to a single computer. The Smart Shooter software does not impose a limit on the number of cameras, but with more than this the USB connection reliability becomes an issue.
When connecting multiple cameras, try to use good quality powered USB hubs and cables. Also experiment with connecting to different USB ports on the computer itself as these can vary in performance. If the computer's own USB ports are supected to be the limiting factor, then try installing a dedicated USB PCIExpress card into the computer.
If you are unable to connect all the cameras to a single computer, then you need to use multiple computers and split the cameras between then. Smart Shooter GRID can then be used to coordinate and control the cameras across multiple computers.