What does the frowning iPod sign mean?

I received my ipod mini as a present about 8 years ago and have been using it for 5 years straight.

I discovered my ipod mini in a junk box but I decided to use it again.

But whenever I press a button after charging it a sign with a ipod making a frown and a ! sign next to it appears. Under the ipod emoticon a url address leads me to apple support.

I'm not able to connect my ipod to itunes nor make the frowning ipod sign go away.

Is it a battery problem? Can I fix it somehow??

Please help!