Accessory Not Supported

I got a brand new InStudio wooden dock for my iPhone 4s for Christmas.
I placed my iPhone on the dock and it immediately started charging. But I got a notification saying "This accessory isn't supported by this device".
When I try to play music through the speaker dock, it doesn't work.
I also tried my moms speaker dock from Sony that worked with my iPod 4. It doesn't work?!
Can somebody help me?

 

But what about the Sony dock?
It says ON THE BOX that it is designed for iPhone 4s.
And the Sony one worked with my iPhone and I gave it to my mom. Three months later it doesn't work with my iPhone?!
Is it due to iOS 8 or something?

 

I have cleaned the port.
I cleaned it a while ago. My phone works in my surround sound system. I place it in the dock cradle and it works for that one. But it doesn't work with these two.
I don't understand. It used to work fine but now it doesn't.