My phone is saying that my official Apple charger is not certified and now I can't charge my phone. What's going on?

I'm using a 5s which I upgraded the OS on a few weeks ago. My charger is in good condition, I've cleaned out the charging port, I don't have a case on the phone, and I've had other people charge their phones with no problem on the same cable. Every time I plug it into my phone it tells me that it's not certified. This is very frustrating.