itunes 12.1.2doesnot reconize ipod in win8.1

See

iPhone, iPad, or iPod not recognized in iTunes for Windows

- I would start with

Removing and reinstalling iTunes and other software components for Windows Vista, Windows 7, or Windows 8

However, after your remove the Apple software components also remove the iCloud Control Panel via Windows Programs and Features app in the Window Control Panel. Then reinstall all the Apple software components

- Then do the other actions of:

iOS: Device not recognized in iTunes for Windows

paying special attention to item #5

- New cable and different USB port

- Run this and see if the results help with determine the cause

iTunes for Windows: Device Sync Tests

Also see:

iPod not recognised by windows iTunes

Troubleshooting issues with iTunes for Windows updates

- Try on another computer to help determine if computer or iPod problem