I bought one of these cheap on trademe,upon turning it on,I realised the operating system doesn't appear stock,so I thought it might be not be charging due too a botched installation? Everything else works.
Android 4.0.3. HTC Sense 4.0 Software Number: Nik Aura Rebirth Sense 4a v3.0 HTC SDK API Level: 4.11 Kernel Version: 3.0.16-g693e8e8 htc-kernel@u18000-build-144 #1 Tue May 29 22:41:32 CST 2012 Baseband Version: 20.4802.30.0822U_3822.10.08.28_M Build Number:1.56.401.2 CL47452 release-keys
(1) Is there any dust/debris in the USB socket? That can prevent the pins from making contact. Give it a good blow out, maybe fish around gently with a bamboo toothpick, and squirt in some isopropyl if you've got some.
(2) Have you tried using another charger? It might be that the charger isn't working correctly.
(3) Have you tried hooking it up to your computer via USB cable? If that doesn't work then the USB port could be fried. You may be able to replace it yourself using a part ordered via eBay. YouTube often has repair videos for popular phones.