Not charging. Lights up momentarily, then goes out

I've been having the same problem where when I plug it in, the blue charging light momentarily goes on, maybe for a maximum of 5 seconds, then goes out.

Do I need a new battery?

I have the same problem with 3 of my vacuums, fixed it by using my rc charger.

Sounds like it. How long have you had the vacuum? That's one of the draw backs of wireless vacuums. On top of providing less than adequate suction, the batteries have poor life spans. I suggest you go back to where you purchased it from and see if they can help you with a new battery