My Photo Stream not working

I have My Photo Stream activated on all my devices, so I expect that when I snap picture with my iPhone, it will appear on my MacBook and iMac in the My Photo Stream folder. It was before, but now it's not. Anybody know why and what can be done to fix this?

Also, when they do appear there (which they did previously) are they in my library on all devices, or do I still have to drag them from MPS to a folder?