Battery does not charge after changing jack and hold button.

Well, I've been looking through the rest of the answers, but any of them fits with my issue so here it goes...

Last week I changed the hold button and headphone jack (the right side of any headphones I connected just didn't work) with the guide and everything went perfectly. The problem has come two days ago, when I realised the iPod showed the battery icon on the top right corner in red, almost finished. Even though I connect it to charge it, it doesn't. I have tried everything I read on some forums, on the official service and even here, but with no results at all.

I don't know if the battery has simply died or the problem can be related with the reconnected circuits inside. What is your recommendation? Should I buy a new battery and change it? Thanks in advance!