I purchased 2 nabi tablets for my grandchildren and they didn't last a month, neither one will hold charge and I even replaced the chargers. I am very disgusted with this product and can I return them for repair or replacement

Try reseting it by holding down the power button (while unpluged,first) for 5-10 seconds. Then plug in charger.

Sounds like you have a good charger/cable, so try resetting the Nabi that's giving you trouble. Hold the power switch down for 10-20 seconds to reset the unit.
I have a couple of NABI-2 tablets and they both react differently to the charging cables; I often have to shut the NABI off completely to charge them. Also, getting the charging cable to connect can be challenging - I will plug the cable in and out several times waiting 10 seconds or so to see if the green LED will go red.

Try a different charger first, as it maybe faulty. If not the battery maybe faulty and I would purchase a new one.

It could be the charger or you may need a new battery.

I fit is a new tablet, I would take it (/send it ) back to supplier and complain and/or ask for a replacement.
If it is not new, then... hmmm.

The original chargers are known to wear out. Fuhu offers to replace (one time) with a more robust cable/charger. After that, ebay has lots of options for chargers and charging cables for the Nabi.

nabi The everything tablet that grows with you

tablet flash red and green

Whenever you plug in your Nabi 2 tablet to charge, The tablet will boot up. Whenever tablet boots up, turn it off and leave it charging for a good 4 to 6 hours. That should charge it.