When the Kindle Oasis looses all charge, it will display a exclamation point on the main screen. I have a PowerCore 10000 that is fully charged and am using the OEM cable. I noticed that when initially charging the Oasis, the yellow charging indicator disappeared after about 30 - 60 seconds. I left it plugged in overnight and in the morning, the yellow charging indicator was still out and I still had an exclamation point. I plugged my charger into my iPhone 6 Plus and verified it was charging and my PC10K power indicator lights are all blue and true.
I then plugged the Oasis charging cable into my laptop and the yellow charging indicator on the Oasis stayed on and then the screen appeared indicating it was taking a charge. I then took the Oasis off the laptop and plugged it back into the PC10K and it is currently charging with a solid yellow charge light.
Why didn't the PC10K charge the Oasis initially and require me to plug it into a laptop USB connector (I am sure any other USB charger would have worked)? I have not reached out to Kindle yet as I wanted to know what the thoughts of the forum are. One of the reasons I have the Oasis is to put documents on it to use in the event of a long term power outage (as it will hold a charge and work for 30 days), but if the PC10K will not charge it from a total power drain, I only have a really small brick that does not meet my needs.