Sorry to hear about the problem with your IRIS+, and welcome to the drone hobby Have you done any firmware updates on your IRIS+ quadcopter? As that would be my first suggestion and then load the default IRIS+ parameters from the PC onto it after the firmware update.
But that error by the sounds of it its possible that the voltage and current sensor on your IRIS+ needs to be calibrated again as a fully charged 3s lipo should be 12.6V. Do you have a multimeter/ battery monitor on hand that you can use to measure your battery voltage? You will also need to get a power analysier (can be found cheaply on ebay) to calibrate your current sensor. But below is a great video showing how to do this calibration if you find that loading the default IRIS+ parameters does not solve the problem.
Hope that helps