Dell Adapter Problem

Hello there helpful people. I'm having a problem with the adapter to my laptop. It's a Dell 65W-AC adapter and came with the laptop I'm using it with. My problem is that it won't charge my battery. It'll power my laptop just fine, as will my battery (when I manage to charge it) but the adapter won't charge anything. Every time I connect it to my laptop I get a pop up error message saying;

"The AC power adapter type cannot be determined. Your system will operate slower and the battery will not charge."

When I first got the laptop barely five months ago the laptop and adapter worked fine together. Like butter and toast. It's only in the past month or two that they stopped cooperating. And I'm iffy on going to the local computer repair places because from previous experience they're not worth anything.

Any help at all is greatly appreciated!