When I plug in my iPad air ,my laptop doesn't recognise. I'm using Windows 8.1 (using Acer V3-571G) but it detecting my Old ipad touch. And the Ipad is not charging when connected to USB port of my laptop

When the iPad is plugged into a computer, it will probably say "Not Charging" because the computer only provides 2.5W of power, whereas the iPad charger provides 10/12W of power. It will charge, but slowly when pkugged into the computer.

iPad not appearing in iTunes

http://www.apple.com/support/ipad/assistant/itunes/

iOS: Device not recognized in iTunes for Mac OS X

http://support.apple.com/kb/TS1591

iOS: Device not recognized in iTunes for Windows

http://support.apple.com/kb/TS1538

iTunes for Windows: iTunes can't contact the iPhone, iPad, or iPod software update server

http://support.apple.com/kb/ts1814

iTunes for Windows: Device Sync Tests

http://support.apple.com/kb/HT4235

IOS: Syncing with iTunes

http://support.apple.com/kb/HT1386

Apple - Support - iPad - Syncing

http://www.apple.com/support/ipad/syncing/

iTunes 10.5 and later: Troubleshooting iTunes Wi-Fi Syncing

http://support.apple.com/kb/ts4062

iOS: "Not enough free space" alert when trying to sync

http://support.apple.com/kb/ts1503

 Cheers, Tom 😉