Ok, problem solved, it wasn't even a matter of broken cable, it was just not well snapped securely into place. The small optical hd cable connection is a little tricky.
Hi, I had a problem with my screen (it was partially green/pink), so I sent the laptop to a technician to change its screen. But before that, I removed the hard drive. When I installed the hd back, I received the message "No Bootable devices found". [IMAGE][IMAGE] (The weird shapes are just the plastic over the new screen). I made a procedure suggested in several places which is change the Boot to Legacy (Secure Boot must be disabled and PTT off). It doesn't work, so I believe I must stick to UEFI: [IMAGE] The hard drive is detected by the BIOS, as it can be seen here (and in fact I could use it normally, but after a turn off / turn on, the problem appeared again): [IMAGE] Since I can get it recognized (sometimes, but sometimes it's not), this makes me think there are no physical problems with the hard drive (it was securely kept stored for 4 days before installed again). The Diagnostic tool showed no problems with the hard drive, but after other tries it shows it's not installed. The only thing I can think is the little cable that is attached to the connection. Are there any additional procedures I should check?
"No Bootable devices found" (Inspiron 15 3576)