Ground Fault Circuit Indicator
One other possibility is you wired the new GFCI incorrectly. There is a difference between line and load. Not all GFCI outlets have the identical "configutation". That is, some have the hot line at the top, others have it at the bottom. Same for the load hot.
At this point, I'd bring in an electrician. No offense, but electricity is dangerous and you have not grasped the basics yet.
BTW - the I stands for Interrupt, not indicator.