now wont start at all

My 2002 V6 mustang won't start. It began right after I got home and now it just clicks a single time (starter). I started troubleshooting by checking the starter relay & fuse, replacing them with no luck. Then I tested the battery myself and it read 12.4V with the car off, not bad but this...

So I desperately need some advice on this one!! So I have an 06 mustang with a newer engine haven’t had many issues with it but recently my car wouldn’t start out of the blue! So I popped the hood and checked a few fuses and as I put about the third fuse back in from checking it my interior...