Starting issue Options

[jaxx6GC]

So one morning I was about to head out and My Celica (5SFE) wouldn't start. I turn the key and all I get is a click, one loud click from the solenoid. I figured my battery was dead so I jumped it with no luck. I've checked over and cleaned all my grounds, tested the battery and starter, rebuilt the starter, replaced it with a new one and replaced the relay. I've also tested the voltage at my starter (Came up with 12+ volts) and still get one loud click when I turn the key. The car was starting fine the day before and I didn't do any work under the hood before this issue arouse. I have noticed that I can engage the starter while the car is running after I bump start it. I'm out of ideas on what could be causing this issue. Does anyone have any ideas on what could be causing this?