The original hard drive stopped working, so I got a new SSD (Crucial MX300, 275GB, part number [CT275MX300SSD1][1]) to put into the MacBook Pro and make a clean install of macOS. Installation of High Sierra using an USB drive looked like it went through well, but when the MacBook Pro rebooted, it got to a screen where it just shows a flashing folder icon with a question mark inside. After that failed, I tried a second time using Network Recovery and installed Mountain Lion. Same flashing folder icon after reboot. NVRAM reset did not fix the issue. After wiping the drive once again, I immediately ran a volume check using Disk Utility and it told me that the volume was damaged. So maybe the issue lies on the SSD itself? [1]: https://www.crucial.com/products/ssd/crucial-mx300-ssd