Cannot use more than two cams?

Hi new here.

Forgive me if this has been addressed elsehwere. Every time I add the third cam it will not appear I get the

‘Cant start video - Try closing other programs that might be using your webcam.’

I’ve checked each cam separately outside of manycam and they all work so its not one particular one that will not work in MCam. Also if I change them around then any two of them will work together but never three? I really need the three for my teaching.

I have the Studio Annual package so should be fine.

I’ve probably overlooked something really stupid but any tips advice would be appreciated please?

I had some issues using USB hubs to connect the cameras, are you using one or each one is on a separate USB port directly on the PC?