Macbook Pro Retina Not Working on Battery, but fully charged and cycle count is low

I have an MBPR (15in) that is about 18 months old (no AppleCare). The battery has only 331 cycles on it, and Apple states it should last for 1000. The battery is fully charged, at 100%.

If I remove the power cord, the machine dies, like the battery is dead -- it completely dies, no sleep.

Consequently, if it is powered off and I turn it on, and then unplug it pretty quickly (before much s/w is loaded) it dies, just the same -- no sleep.

The light is green on the charger and the battery status shows 100%, but it also says it needs to be replaced. I tend to think the battery itself does not need to be replaced yet, but that something is preventing the machine from using the battery.

In About this Mac reports:

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  7377 charge remaining (100%),

  
  


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  fully charged: yes,

  
  


• 
  

  charging: no,

  
  


• 
  

  full charge capacity: 7450.

  
  

Does anyone have any knowledge of issues with this? I hate to have to sink money in this very well cared for MBPR.

FWIW I have tried an SMC reset and PRAM reset, a few times, ea.