My iphone 6 says the factory charger is not supported and wont charge?

Either the cable Lightning connector or the jack on the phone is dirty. Clean the connector with electrical contact cleaner. Clean the jack by first blowing it out with canned compressed gas - NEVER by mouth, and contact clearer if necessary.

It may need to be plugged into a computer with the cable and the Apple software, on the computer you usually use (has your itunes on it), may need updating. I am trying this right now. It's charging the iphone now. I have an iPhone 6s. I'll try to remember to come back here and say whether I could go back to using the charger block later on.