The discs are not being charged in the stack.

Make sure all power cables are properly connected at each point (wall, adapter brick, Walker base). 

Make sure you have pressed the button on the base to power it up. 

When trying to charge a phone, make sure the on/off button on top of the disc has been pressed - this will make it light up blue. 

If still not charging, the issue is most likely the power adapter, contact Chargebar to organsie a replacement.