I had this same problem. Plugged in the power chord, blue light flickers, if I turn the chord a little bit it gets stable (makes contact) and then after a few seconds blue light off. I first thought the problem was just poor contact, which is a PROBLEM in my case because if flickers at first, but not the main problem as the light goes stable after good contact and them off after a few seconds.
As it turns out this model comes with a RED plastic protector, some king of plastic plugg to protect the DC socket. It's a small individual part you can put it in when you are not using and take out to use the trimmer.
When that plastic RED protector is plugged it protects agains water/humidity/etc AND the trimmer won't turn on. The same when you are charging, the trimmer won't work. So, I found that when you plug something in the DC socket there's a very small mechanical switch inside that prevents the trimmer to work.
So back to the beginning, the blue light goes off after a few seconds meaning the battery is fully charged. You plugg out the power chord and nothing. WHY? Because the mechanical switch is ON, in my case it was jammed, stuck in that position. I opened it all, did a bypass to that mechanical switch and VOILA, everything working normally.
So, what is my problem right now? I worked around the mechanical switch thing, but sometimes it does not charge, because the DC connector is bad, after me trying to clean it, end up forcing it, as I thought it was a calcination problem (not sure if this is the right term, calcination), I mean full of grey dust which prevents a good contact.
SO, now I need to replace the DC socket BUT don't know which type/size is it to look for it for example in ebay.
Does anyone now what type of DC SOCKET is it? Any reference? DC-003 maybe?