Is it possible that you trimmed more than the tray and took out a functional part of the hard drive by accident?
If you put the drive back into a PC and read it look for files and drive sizes, if something is on there and it's functional and the files are readable, you might want to run checkdisk on it or something.
Weird that you didn't need to unlock it first, but it's possible that someone either unlocked it before you ever got the unit or there is something wrong with this drive and they tried to lock it and didn't check it.
And I didn't need to take mine out of the tray to get it to read and plug into the PC. What kind of adapter did you use?
I would focus on the HDD door, that sounds like what happens when that is not put on all the way. Maybe your switch went bad or something. But if the door is not on, that's what it sounds like what will happen. If you take out the hard drive and then close the door and screw it in with no hard drive in the unit, will the unit boot up?