Why are the fish not biting??

Lately I have struggled heavily to pull fish out of the water at the lake.  I have tried everything in my tackle box to see what the fish will bite.  Carolina rig, texas rig, swimbait, crank bait, you name it I have thrown in the water and haven't even got a look I don't think from the fish.  While im casting and reeling, I have differents thoughts run through my head.  A thought that maybe I am fishing the wrong lake.  The lake I normally fish is Lake Robinson in Greer.  I have fished there for a few years and have found a few spots that are always worth a try because I always catch a few in those spots. But when those spots aren't working, I know its not just me.  Another main key I saw was when I pulled up to the lake, there were no boats in the parking lot, a first for me.  Maybe when the weather gets a little bit cooler, the fish will jump back on my hook.