MKRZero not responding to LiPo battery via port

I connect a LiPo battery to the MRkZero via the battery port and no light...nothing.
i directly connect the battery to VIN/GRD pins and works perfectly.

I saw one old post where someone said the solution was 'swaping' the polarity of the LiPo battery?
I'm unsure how to do this?

Thanks

Actually, when I connect the Adafruit 1200mAh battery to
-Battery port nothing happens

  • VIN & GRD some lights come on; the charge light glows dimly; MKRZero does not run
    this is the case with 2 MKRZeros that I've purchased?
    I'm definitely doing something wrong
    Can anyone help?
    Thanks

Some connectors on the Li-ion batteries are swapped. See the red and black wire? Cut it in the middle and swapped the connection.

Yes I bought one battery and the connectors were switched
Fortunately I have a bag of connectors and rewired blk to red and red to blk
but still no response from either of my MKRZeros
Thank you

Also batteries test 4.18V for the 1200 mAh and 3.76 v for the 3700 mAh
So batteries are good