What does this ipod message mean exactly

I put on of my old iPods on the computer to charge And when i did I got this message The ipod D'S IPOD cannot be synced because it cannot be read from or written to. I tried to update the ipod but it said it was up to date It is hooked up I see the icon for it on iTunes and I click and play a song from the iPod iTunes says 5 iPod are allowed on this computer and this is one of them

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