I have 3 Mavic Pro Batteries. 2 Are Dead, wont charge and wont turn on at all.

3rd one when I plug it in the 1st Light blinks 3 times but wont charge. I have tried single charging, Hub charging, holding button for 30 seconds, etc. Nothing has worked.
Any suggestions? Or is my only option to just send them back to DJI to be replaced or repaired for a fee?

Ben,
Sorry to hear about your battery problem.

Are these new or used batteries?
If used ,How many charges did they have?

Did they all fail at the same time?
Or over time?

Could your charger be bad?
Do you have another charger to try?

Hopefully you will get an answer to your problem from the forum or a DJI admin.
If all else fails I would get in touch with DJI service for advise.

I do have a 4th Battery that I use that works fine and charges fine so I dont think it is the charger. The only thing I can think of is I let them sit too long without being used/charged.

Hi, we're sorry to know about this situation. I would like to clarify for how long did you charge those batteries? If the batteries are not responding, I would recommend contacting our support using the link below. The warranty would depend on the product if it's still within the warranty and the outcome of the evaluation of our designated department. You may refer to the link below for our after sales policy and warranty period of our DJI Products.

www.dji.com/support

https://www.dji.com/service/policy