Because the bottom is putting pressure on something that is causing it to malfunction. The more significant question is why did it work before you took it apart while now it doesn't. You spilled coffee on it. Perhaps something has failed or been damaged. I don't have an answer, but I've asked the right question.
Having spilled coffee in the machine is a possible death warrant if it has gotten onto the motherboard or in other parts of the computer. Especially since you took so long before deciding to clean it. You should have rushed it to your local Apple shop immediately after the spill.
I realize I should have cleaned it right away, but I didn't. As for my "local" apple store, probably 8 hours away.
I wanted to find out if anyone else had a similar problem, as you say the bottom lid is probably putting pressure on a component causing it to fail. I know it could be anything, but I was only curious if someone possibly knew of something to look for or to change.
Thanks for your help.
coffee would not HAVE to do anything except mechanically. It would not have any effect now since it has dried out, well short of corroding some components.
Check the points where the HDD casing "meets" the Macbook casing. How much pressure is there?
What about the pressure pins "pogo pins" are they all functioning?
What about pressure on the cables?
Please describe how it wont boot? What exactly does it do / happens
Try booting lid on, in Verbose mode. Hold down CMD V
Then watch as it lists on the s Rene what is happening. Then take note (I take pictures) of what is the last thing it does, where it crashes or stops.
Could it be coffee in the SATA cable, that is sort of on one side of the connector so that when lid is on that side is the only one pressing and making copper contact. Looooong shot this one
Check the ifixit.com repair manual to see all the wires and where they are located so you know where to look inside for pressure points