This is likely to be a cable issue, you can actually unplug the Devonshire's cables to test them.
Simply pull on the offending cable to unplug it from its secure USB port, and test it with a different USB port to see if it works to charge a phone. If it works, the issue is the disc's port, which should then be tested with a working cable to 100% confirm.
Make sure the disc is actually activated - just press the on/off button on top of the disc, which will make it light up blue, and turn it on.
If the cable is still not charging a phone, you can purchase a replacement cable, or a cable pack for added value, from Chargebar's website.